Thermostat with power stealing delay interval at transitions between power stealing states

ABSTRACT

A thermostat includes a plurality of HVAC (heating, ventilation, and air conditioning) wire connectors including a connection to at least one call relay wire. The thermostat may also include a powering circuit, including a rechargeable battery, which is configured to provide electrical power to the thermostat by power stealing from a selected call relay wire. The power stealing may comprise an active power stealing mode, in which power is taken from the same selected call relay wire that is used to call for an HVAC function, and an inactive power stealing mode in which, in which no active call is being made. The powering circuit may be configured to substantially suspend (or at least reduce the level of) power stealing for at least a first time period following each transition of the thermostat from between operating states.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/293,915 (Attorney Docket No. 94021-908864) filed Jun. 2, 2014, whichis a continuation of U.S. application Ser. No. 13/958,191 (AttorneyDocket No. 94021-882627) filed Aug. 2, 2013, now U.S. Pat. No.8,770,491, which is a continuation of U.S. application Ser. No.13/601,574 (Attorney Docket No. 94021-847942) filed Aug. 31, 2012, nowU.S. Pat. No. 8,511,577, which is a continuation-in-part (CIP) of U.S.application Ser. No. 13/467,025 (Attorney Docket No. 94021-827457),filed May 8, 2012, now U.S. Pat. No. 8,788,103, which claims the benefitof U.S. Provisional Application No. 61/627,996 (Attorney Docket No.NES0101-PROV) filed Oct. 21, 2011.

U.S. Ser. No. 13/467,025 (Attorney Docket No. 94021-827457) is also acontinuation-in-part of the following commonly-assigned applications:PCT Application No. PCT/US11/61437, (Attorney Docket No. NES0101-PCT)filed Nov. 18, 2011; U.S. Ser. No. 13/267,877, (Attorney Docket No.94021-856455), filed Oct. 6, 2011, now U.S. Pat. No. 9,026,254; U.S.Ser. No. 13/034,674 (Attorney Docket No. 94021-856074) filed Feb. 24,2011; and U.S. Ser. No. 13/034,678 (Attorney Docket No. 94021-856076)filed Feb. 24, 2011, now U.S. Pat. No. 8,752,771.

Each of the above-referenced patent applications is incorporated hereinby reference in its entirety for all purposes.

TECHNICAL FIELD

This patent specification relates to systems and methods for themonitoring and control of energy-consuming systems or otherresource-consuming systems. More particularly, this patent specificationrelates control units that govern the operation of energy-consumingsystems, household devices, or other resource-consuming systems,including methods for providing electrical power for thermostats thatgovern the operation of heating, ventilation, and air conditioning(HVAC) systems.

BACKGROUND OF THE INVENTION

Substantial effort and attention continue toward the development ofnewer and more sustainable energy supplies. The conservation of energyby increased energy efficiency remains crucial to the world's energyfuture. According to an October 2010 report from the U.S. Department ofEnergy, heating and cooling account for 56% of the energy use in atypical U.S. home, making it the largest energy expense for most homes.Along with improvements in the physical plant associated with homeheating and cooling (e.g., improved insulation, higher efficiencyfurnaces), substantial increases in energy efficiency can be achieved bybetter control and regulation of home heating and cooling equipment.

As is known, for example as discussed in the technical publication No.50-8433, entitled “Power Stealing Thermostats” from Honeywell (1997),early thermostats used a bimetallic strip to sense temperature andrespond to temperature changes in the room. The movement of thebimetallic strip was used to directly open and close an electricalcircuit. Power was delivered to an electromechanical actuator, usuallyrelay or contactor in the HVAC equipment whenever the contact was closedto provide heating and/or cooling to the controlled space. Since thesethermostats did not require electrical power to operate, the wiringconnections were very simple. Only one wire connected to the transformerand another wire connected to the load. Typically, a 24 VAC power supplytransformer, the thermostat, and 24 VAC HVAC equipment relay were allconnected in a loop with each device having only two externalconnections required.

When electronics began to be used in thermostats the fact that thethermostat was not directly wired to both sides of the transformer forits power source created a problem. This meant either the thermostat hadto have its own independent power source, such as a battery, or behardwired directly from the system transformer. Direct hardwiring a“common” wire from the transformer to the electronic thermostat may bevery difficult and costly. However, there are also disadvantages tousing a battery for providing the operating power. One primarydisadvantage is the need to continually check and replace the battery.If the battery is not properly replaced and cannot provide adequatepower, the electronic thermostat may fail during a period of extremeenvironmental conditions.

Because many households do not have a direct wire from the systemtransformer (such as a “common” wire), some thermostats have beendesigned to derive power from the transformer through the equipmentload. The methods for powering an electronic thermostat from thetransformer with a single direct wire connection to the transformer arecalled “power stealing” or “power sharing.” The thermostat “steals,”“shares” or “harvests” its power during the “OFF” periods of the heatingor cooling system by allowing a small amount of current to flow throughit into the load coil below its response threshold (even at maximumtransformer output voltage). During the “ON” periods of the heating orcooling system the thermostat draws power by allowing a small voltagedrop across itself. Ideally, the voltage drop will not cause the loadcoil to dropout below its response threshold (even at minimumtransformer output voltage). Examples of thermostats with power stealingcapability include the Honeywell T8600, Honeywell T8400C, and theEmerson Model 1F97-0671. However, these systems do not have powerstorage means and therefore must always rely on power stealing or mustuse disposable batteries.

Additionally, microprocessor controlled “intelligent” thermostats mayhave more advanced environmental control capabilities that can saveenergy while also keeping occupants comfortable. To do this, thesethermostats require more information from the occupants as well as theenvironments where the thermostats are located. These thermostats mayalso be capable of connection to computer networks, including both localarea networks (or other “private” networks) and wide area networks suchas the Internet (or other “public” networks), in order to obtain currentand forecasted outside weather data, cooperate in so-calleddemand-response programs (e.g., automatic conformance with power alertsthat may be issued by utility companies during periods of extremeweather), enable users to have remote access and/or control thereofthrough their network-connected device (e.g., smartphone, tabletcomputer, PC-based web browser), and other advanced functionalities thatmay require network connectivity.

Issues arise in relation to providing microprocessor-controlled,network-connected thermostats, one or more such issues being at leastpartially resolved by one or more of the embodiments describedhereinbelow. On the one hand, it is desirable to provide a thermostathaving advanced functionalities such as those associated with relativelypowerful microprocessors and reliable wireless communications chips,while also providing a thermostat that has an attractive, visuallypleasing electronic display that users will find appealing to behold andinteract with. On the other hand, it is desirable to provide athermostat that is compatible and adaptable for installation in a widevariety of homes, including a substantial percentage of homes that arenot equipped with the “common” wire discussed above. It is still furtherdesirable to provide such a thermostat that accommodates easydo-it-yourself installation such that the expense and inconvenience ofarranging for an HVAC technician to visit the premises to install thethermostat can be avoided for a large number of users. It is stillfurther desirable to provide a thermostat having such processing power,wireless communications capabilities, visually pleasing displayqualities, and other advanced functionalities, while also being athermostat that, in addition to not requiring a “common” wire, likewisedoes not require to be plugged into household line current or aso-called “power brick,” which can be inconvenient for the particularlocation of the thermostat as well as unsightly.

BRIEF SUMMARY OF THE INVENTION

In one embodiment, a thermostat is presented. The thermostat may includea plurality of HVAC (heating, ventilation, and air conditioning) wireconnectors configured to receive a plurality of HVAC wires, where theplurality of HVAC wires is associated with an HVAC system, and theplurality of HVAC wires comprises at least one call relay wire. Thethermostat may also include a powering circuit, including a rechargeablebattery, which is coupled to the plurality of HVAC wire connectors. Thepowering circuit may be configured to provide electrical power to thethermostat by power stealing from a selected one of the at least onecall relay wires. The power stealing may include an active powerstealing mode in which power is taken from the selected call relay wirewhile the thermostat is in a first operating mode in which thethermostat is actively calling for an HVAC function associated with theselected call relay wire. The power stealing may also include aninactive power stealing mode in which power is taken from the selectedcall relay wire while the thermostat is in a second operating mode inwhich the thermostat is not actively calling for the HVAC functionassociated with the selected call relay wire. The powering circuit canbe configured to substantially suspend power stealing for at least afirst time period immediately following: (i) each transition of thethermostat from the first operating mode to the second operating mode;and (ii) each transition of the thermostat from the second operatingmode to the first operating mode. The powering circuit can provide theelectrical power to the thermostat during times of substantiallysuspended power stealing at least in part by drawing power from therechargeable battery.

In one embodiment, the suspended power stealing may include stealing afirst amount of power that is substantially less than a second amount ofpower that is stolen during times when said power stealing is notsuspended. In another embodiment, during the active power stealing modea connection between (i) the selected call relay wire and (ii) acorresponding return HVAC wire is disconnected for periods lasting atleast a second time period. The second time period during which theconnection is disconnected may be substantially less than a third timeperiod during which the connection is connected during the active powerstealing mode. In one embodiment, the thermostat can further beconfigured to detect an absence of a common “C” wire coupled to theplurality of HVAC wire connectors. The thermostat can also be furtherconfigured to select the selected call relay wire during the absence. Inanother embodiment the thermostat can be further configured to detect acommon “C” wire coupled to the plurality of HVAC wire connectors, andthe power stealing can be suspended when the common “C” wire isdetected.

In one embodiment, the first time period may comprise betweenapproximately 5 seconds and approximately 20 seconds when the thermostattransitions from the first operating mode to the second operating mode.In another embodiment the first time period may comprise betweenapproximately 40 seconds and approximately 160 seconds when thethermostat transitions from the second operating mode to the firstoperating mode. The suspended power stealing may comprise reducing acurrent associated with the power that is stolen to less thanapproximately 1 mA. Furthermore, the powering circuit can be configuredto select a “Y” wire as the selected call relay wire when the HVACsystem is in an active heating state. Also, the powering circuit can beconfigured to select a “W” wire as the selected call relay wire when theHVAC system is in an active cooling state.

In another embodiment, a method of controlling an HVAC system using athermostat is presented. The method may include selecting a call relaywire from a plurality of HVAC wire connectors configured to receive aplurality of HVAC wires, where the plurality of HVAC wires is associatedwith an HVAC system, and the plurality of HVAC wires comprises at leastone call relay wire. The method may also include providing electricalpower to the thermostat by power stealing from said selected call relaywire. In one embodiment, the power stealing may include an active powerstealing mode in which power is taken from the selected call relay wirewhile the thermostat is in a first operating mode in which thethermostat is actively calling for an HVAC function associated with theselected call relay wire. In one embodiment, the power stealing mayfurther include an inactive power stealing mode in which power is takenfrom the selected call relay wire while the thermostat is in a secondoperating mode in which the thermostat is not actively calling for saidHVAC function associated with the selected call the wire. The method mayadditionally include detecting transitions of the thermostat (i) fromsaid first operating mode to the second operating mode, and (ii) fromthe second operating mode to the first operating mode. The method mayfurther include substantially suspending the power stealing for at leasta first time period immediately following each detected transition. Theelectrical power can be provided to the thermostat during times ofsubstantially suspended power stealing at least in part by drawing powerfrom a rechargeable battery.

In one embodiment, the first time period may comprise approximately 10seconds when the thermostat transitions from the first operating mode tothe second operating mode. In another embodiment, the first time periodmay comprise approximately 75 seconds when the thermostat transitionsfrom the second operating mode to the first operating mode. In anotherembodiment, the suspended power stealing may comprise reducing a currentassociated with the power that is stolen to less than approximately 5mA. In yet another embodiment, the suspended power stealing may comprisereducing a current associated with the power that is stolen toapproximately 0 mA. Also, the method may further include detecting anabsence of a common “C” wire coupled to the plurality of HVAC wireconnectors.

In yet another embodiment, a thermostat is presented. The thermostat mayinclude a first HVAC wire connector configured to receive an HVAC callrelay wire of an HVAC system. In one embodiment, the HVAC system isconfigured to operate in at least two states, including an active state,where the thermostat activates an HVAC function using the first HVACwire connector, and an inactive state, where the thermostat deactivatesthe HVAC function using the first HVAC wire connector. The thermostatmay also include a powering circuit coupled to the first HVAC wireconnector and configured to steal power from the HVAC system. In oneembodiment, the powering circuit may include a rechargeable batteryconfigured to store power stolen from the HVAC system, and a controlcircuit. In one embodiment, the control circuit may be configured to:(i) determine that the HVAC system is transitioning from the activestate to the inactive state, and in response, cause a power level thatis stolen from the HVAC system to be reduced for a first time period;and (i) determine that the HVAC system is transitioning from theinactive state to the active state, and in response, cause the powerlevel that is stolen from the HVAC system to be reduced for a secondtime period.

In one embodiment, the HVAC function may include a heating functionduring the active state, where the first HVAC wire connector is coupledto a “W” wire. The HVAC function may also include a cooling functionduring the active state, where the first HVAC wire connector is coupledto a “Y” wire. In one embodiment, the thermostat can be furtherconfigured to detect a presence of a common “C” wire coupled to a secondHVAC wire connector, and cause the first time period to be substantially0 seconds and the second time period to be substantially 0 seconds. Inanother embodiment, the first time period may comprise betweenapproximately 5 seconds and approximately 20 seconds, and the secondtime period may comprise between approximately 40 seconds andapproximately 160 seconds.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings. Also note that other embodiments may bedescribed in the following disclosure and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an enclosure with an HVAC system, according tosome embodiments;

FIG. 2 is a diagram of an HVAC system, according to some embodiments;

FIG. 3A is a schematic block diagram that provides an overview of somecomponents inside a thermostat in accordance with embodiments of thepresent invention;

FIG. 3B is a block diagram of some circuitry of a thermostat, accordingto some embodiments;

FIGS. 4A-4C schematically illustrate the use of auto-switchingconnectors being used to automatically select a source for powerharvesting, according to some embodiments;

FIG. 5 is a schematic of a half-bridge sense circuit, according to someembodiments;

FIGS. 6A-6B are schematics showing the high voltage buck, bootstrap LDOand battery LDO power circuitry, according to some embodiments;

FIG. 6C shows a battery charging circuit and rechargeable battery,according to some embodiments;

FIG. 7 illustrates an exploded perspective view of a versatile sensingand control unit (VSCU unit) and an HVAC-coupling wall dock according toan embodiment;

FIGS. 8A-8B illustrates conceptual diagrams of HVAC-coupling wall docks,according to some embodiments;

FIGS. 9A-9B illustrate a thermostat having a user-friendly interface,according to some embodiments;

FIG. 9C illustrates a cross-sectional view of a shell portion of a frameof the thermostat of FIGS. 9A-9B;

FIGS. 10A-10B illustrate exploded front and rear perspective views,respectively, of a thermostat with respect to its two main components,which are the head unit and the back plate;

FIGS. 11A-11B illustrate exploded front and rear perspective views,respectively, of the head unit with respect to its primary components;

FIGS. 12A-12B illustrate exploded front and rear perspective views,respectively, of the head unit frontal assembly with respect to itsprimary components;

FIGS. 13A-13B illustrate exploded front and rear perspective views,respectively, of the backplate unit with respect to its primarycomponents;

FIG. 14 illustrates a perspective view of a partially assembled headunit front, according to some embodiments;

FIG. 15 illustrates a head-on view of the head unit circuit board,according to one embodiment;

FIG. 16 illustrates a rear view of the backplate circuit board,according to one embodiment;

FIGS. 17A-17C illustrate conceptual examples of the sleep-wake timingdynamic, at progressively larger time scales; according to oneembodiment;

FIG. 18 illustrates a self-descriptive overview of the functionalsoftware, firmware, and/or programming architecture of the head unitmicroprocessor, according to one embodiment;

FIG. 19 illustrates a self-descriptive overview of the functionalsoftware, firmware, and/or programming architecture of the backplatemicrocontroller, according to one embodiment;

FIG. 20 illustrates a thermostat according to a preferred embodiment;

FIG. 21 illustrates a flowchart of a method for using a delay intervalduring transitions between operating states while power stealing,according to one embodiment, and

FIG. 22 illustrates a flowchart of another method for using a delayinterval during transitions between operating states while powerstealing, according to one embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter of this patent specification relates to the subjectmatter of the following commonly assigned applications, each of which isincorporated by reference herein: U.S. Ser. No. 12/881,430 filed Sep.14, 2010; U.S. Ser. No. 12/881,463 filed Sep. 14, 2010; U.S. Prov. Ser.No. 61/415,771 filed Nov. 19, 2010; U.S. Prov. Ser. No. 61/429,093 filedDec. 31, 2010; U.S. Ser. No. 12/984,602 filed Jan. 4, 2011; U.S. Ser.No. 12/987,257 filed Jan. 10, 2011; U.S. Ser. No. 13/033,573 filed Feb.23, 2011; U.S. Ser. No. 29/386,021, filed Feb. 23, 2011; U.S. Ser. No.13/034,666 filed Feb. 24, 2011; U.S. Ser. No. 13/034,674 filed Feb. 24,2011; U.S. Ser. No. 13/034,678 filed Feb. 24, 2011; U.S. Ser. No.13/038,191 filed Mar. 1, 2011; U.S. Ser. No. 13/038,206 filed Mar. 1,2011; U.S. Ser. No. 29/399,609 filed Aug. 16, 2011; U.S. Ser. No.29/399,614 filed Aug. 16, 2011; U.S. Ser. No. 29/399,617 filed Aug. 16,2011; U.S. Ser. No. 29/399,618 filed Aug. 16, 2011; U.S. Ser. No.29/399,621 filed Aug. 16, 2011; U.S. Ser. No. 29/399,623 filed Aug. 16,2011; U.S. Ser. No. 29/399,625 filed Aug. 16, 2011; U.S. Ser. No.29/399,627 filed Aug. 16, 2011; U.S. Ser. No. 29/399,630 filed Aug. 16,2011; U.S. Ser. No. 29/399,632 filed Aug. 16, 2011; U.S. Ser. No.29/399,633 filed Aug. 16, 2011; U.S. Ser. No. 29/399,636 filed Aug. 16,2011; U.S. Ser. No. 29/399,637 filed Aug. 16, 2011; U.S. Ser. No.13/199,108, filed Aug. 17, 2011; U.S. Ser. No. 13/267,871 filed Oct. 6,2011; U.S. Ser. No. 13/267,877 filed Oct. 6, 2011; U.S. Ser. No.13/269,501, filed Oct. 7, 2011; U.S. Ser. No. 29/404,096 filed Oct. 14,2011; U.S. Ser. No. 29/404,097 filed Oct. 14, 2011; U.S. Ser. No.29/404,098 filed Oct. 14, 2011; U.S. Ser. No. 29/404,099 filed Oct. 14,2011; U.S. Ser. No. 29/404,101 filed Oct. 14, 2011; U.S. Ser. No.29/404,103 filed Oct. 14, 2011; U.S. Ser. No. 29/404,104 filed Oct. 14,2011; U.S. Ser. No. 29/404,105 filed Oct. 14, 2011; U.S. Ser. No.13/275,307 filed Oct. 17, 2011; U.S. Ser. No. 13/275,311 filed Oct. 17,2011; U.S. Ser. No. 13/317,423 filed Oct. 17, 2011; U.S. Ser. No.13/279,151 filed Oct. 21, 2011; U.S. Ser. No. 13/317,557 filed Oct. 21,2011; U.S. Prov. Ser. No. 61/627,996 filed Oct. 21, 2011; PCT/US11/61339filed Nov. 18, 2011; PCT/US11/61344 filed Nov. 18, 2011; PCT/US11/61365filed Nov. 18, 2011; PCT/US11/61379 filed Nov. 18, 2011; PCT/US11/61391filed Nov. 18, 2011; PCT/US11/61479 filed Nov. 18, 2011; PCT/US11/61457filed Nov. 18, 2011; PCT/US11/61470 filed Nov. 18, 2011; PCT/US11/61339filed Nov. 18, 2011; PCT/US11/61491 filed Nov. 18, 2011; PCT/US11/61437filed Nov. 18, 2011; PCT/US11/61503 filed Nov. 18, 2011; U.S. Ser. No.13/342,156 filed Jan. 2, 2012; PCT/US12/00008 filed Jan. 3 2012;PCT/US12/20088 filed Jan. 3, 2012; PCT/US12/20026 filed Jan. 3, 2012;PCT/US12/00007 filed Jan. 3, 2012; U.S. Ser. No. 13/351,688 filed Jan.17, 2012; U.S. Ser. No. 13/356,762 filed Jan. 24, 2012; PCT/US12/30084filed Mar. 22, 2012; U.S. Ser. No. 13/434,573 filed Mar. 29, 2012; U.S.Ser. No. 13/434,560 filed Mar. 29, 2012; U.S. Ser. No. 13/440,907 filedApr. 5, 2012; and U.S. Ser. No. 13/440,910 filed Apr. 5, 2012. Theabove-referenced patent applications are collectively referenced hereinas “the commonly assigned incorporated applications.”

In the following detailed description, for purposes of explanation,numerous specific details are set forth to provide a thoroughunderstanding of the various embodiments of the present invention. Thoseof ordinary skill in the art will realize that these various embodimentsof the present invention are illustrative only and are not intended tobe limiting in any way. Other embodiments of the present invention willreadily suggest themselves to such skilled persons having the benefit ofthis disclosure.

In addition, for clarity purposes, not all of the routine features ofthe embodiments described herein are shown or described. One of ordinaryskill in the art would readily appreciate that in the development of anysuch actual embodiment, numerous embodiment-specific decisions may berequired to achieve specific design objectives. These design objectiveswill vary from one embodiment to another and from one developer toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming but would nevertheless be a routineengineering undertaking for those of ordinary skill in the art havingthe benefit of this disclosure.

It is to be appreciated that while one or more embodiments are describedfurther herein in the context of typical HVAC system used in aresidential home, such as single-family residential home, the scope ofthe present teachings is not so limited. More generally, thermostatsaccording to one or more of the preferred embodiments are applicable fora wide variety of enclosures having one or more HVAC systems including,without limitation, duplexes, townhomes, multi-unit apartment buildings,hotels, retail stores, office buildings and industrial buildings.Further, it is to be appreciated that while the terms user, customer,installer, homeowner, occupant, guest, tenant, landlord, repair person,and the like may be used to refer to the person or persons who areinteracting with the thermostat or other device or user interface in thecontext of one or more scenarios described herein, these references areby no means to be considered as limiting the scope of the presentteachings with respect to the person or persons who are performing suchactions.

Provided according to one or more embodiments are systems, methods,computer program products, and related business methods for controllingone or more HVAC systems based on one or more versatile sensing andcontrol units (VSCU units), each VSCU unit being configured and adaptedto provide sophisticated, customized, energy-saving HVAC controlfunctionality while at the same time being visually appealing,non-intimidating, elegant to behold, and delightfully easy to use. Theterm “thermostat” is used hereinbelow to represent a particular type ofVSCU unit (Versatile Sensing and Control) that is particularlyapplicable for HVAC control in an enclosure. Although “thermostat” and“VSCU unit” may be seen as generally interchangeable for the contexts ofHVAC control of an enclosure, it is within the scope of the presentteachings for each of the embodiments hereinabove and hereinbelow to beapplied to VSCU units having control functionality over measurablecharacteristics other than temperature (e.g., pressure, flow rate,height, position, velocity, acceleration, capacity, power, loudness,brightness) for any of a variety of different control systems involvingthe governance of one or more measurable characteristics of one or morephysical systems, and/or the governance of other energy or resourceconsuming systems such as water usage systems, air usage systems,systems involving the usage of other natural resources, and systemsinvolving the usage of various other forms of energy.

FIG. 1 is a diagram illustrating an exemplary enclosure using athermostat 110 implemented in accordance with the present invention forcontrolling one or more environmental conditions. For example, enclosure100 illustrates a single-family dwelling type of enclosure using alearning thermostat 110 (also referred to for convenience as “thermostat110”) for the control of heating and cooling provided by an HVAC system120. Alternate embodiments of the present invention may be used withother types of enclosures including a duplex, an apartment within anapartment building, a light commercial structure such as an office orretail store, or a structure or enclosure that is a combination of theseand other types of enclosures.

Some embodiments of thermostat 110 in FIG. 1 incorporate one or moresensors to gather data from the environment associated with enclosure100. Sensors incorporated in thermostat 110 may detect occupancy,temperature, light and other environmental conditions and influence thecontrol and operation of HVAC system 120. Sensors incorporated withinthermostat 110 do not protrude from the surface of the thermostat 110thereby providing a sleek and elegant design that does not drawattention from the occupants in a house or other enclosure. As a result,thermostat 110 and readily fits with almost any décor while adding tothe overall appeal of the interior design.

As used herein, a “learning” thermostat refers to a thermostat, or oneof plural communicating thermostats in a multi-thermostat network,having an ability to automatically establish and/or modify at least onefuture setpoint in a heating and/or cooling schedule based on at leastone automatically sensed event and/or at least one past or current userinput.

As used herein, a “primary” thermostat refers to a thermostat that iselectrically connected to actuate all or part of an HVAC system, such asby virtue of electrical connection to HVAC control wires (e.g. W, G, Y,etc.) leading to the HVAC system.

As used herein, an “auxiliary” thermostat refers to a thermostat that isnot electrically connected to actuate an HVAC system, but that otherwisecontains at least one sensor and influences or facilitates primarythermostat control of an HVAC system by virtue of data communicationswith the primary thermostat.

In one particularly useful scenario, the thermostat 110 is a primarylearning thermostat and is wall-mounted and connected to all of the HVACcontrol wires, while the remote thermostat 112 is an auxiliary learningthermostat positioned on a nightstand or dresser, the auxiliary learningthermostat being similar in appearance and user-interface features asthe primary learning thermostat, the auxiliary learning thermostatfurther having similar sensing capabilities (e.g., temperature,humidity, motion, ambient light, proximity) as the primary learningthermostat, but the auxiliary learning thermostat not being connected toany of the HVAC wires. Although it is not connected to any HVAC wires,the auxiliary learning thermostat wirelessly communicates with andcooperates with the primary learning thermostat for improved control ofthe HVAC system, such as by providing additional temperature data at itsrespective location in the enclosure, providing additional occupancyinformation, providing an additional user interface for the user, and soforth.

It is to be appreciated that while certain embodiments are particularlyadvantageous where the thermostat 110 is a primary learning thermostatand the remote thermostat 112 is an auxiliary learning thermostat, thescope of the present teachings is not so limited. Thus, for example,while certain initial provisioning methods that automatically pairassociate a network-connected thermostat with an online user account areparticularly advantageous where the thermostat is a primary learningthermostat, the methods are more generally applicable to scenariosinvolving primary non-learning thermostats, auxiliary learningthermostats, auxiliary non-learning thermostats, or other types ofnetwork-connected thermostats and/or network-connected sensors. By wayof further example, while certain graphical user interfaces for remotecontrol of a thermostat may be particularly advantageous where thethermostat is a primary learning thermostat, the methods are moregenerally applicable to scenarios involving primary non-learningthermostats, auxiliary learning thermostats, auxiliary non-learningthermostats, or other types of network-connected thermostats and/ornetwork-connected sensors. By way of even further example, while certainmethods for cooperative, battery-conserving information polling of athermostat by a remote cloud-based management server may be particularlyadvantageous where the thermostat is a primary learning thermostat, themethods are more generally applicable to scenarios involving primarynon-learning thermostats, auxiliary learning thermostats, auxiliarynon-learning thermostats, or other types of network-connectedthermostats and/or network-connected sensors.

Enclosure 100 further includes a private network accessible bothwirelessly and through wired connections and may also be referred to asa Local Area Network or LAN. Network devices on the private networkinclude a computer 124, thermostat 110 and remote thermostat 112 inaccordance with some embodiments of the present invention. In oneembodiment, the private network is implemented using an integratedrouter 122 that provides routing, wireless access point functionality,firewall and multiple wired connection ports for connecting to variouswired network devices, such as computer 124. Each device is assigned aprivate network address from the integrated router 122 eitherdynamically through a service like Dynamic Host Configuration Protocol(DHCP) or statically through actions of a network administrator. Theseprivate network addresses may be used to allow the devices tocommunicate with each directly over the LAN. Other embodiments mayinstead use multiple discrete switches, routers and other devices (notshown) to perform more other networking functions in addition tofunctions as provided by integrated router 122.

Integrated router 122 further provides network devices access to apublic network, such as the Internet, provided enclosure 100 has aconnection to the public network generally through a cable-modem, DSLmodem and an Internet service provider or provider of other publicnetwork service. Public networks like the Internet are sometimesreferred to as a Wide-Area Network or WAN. In the case of the Internet,a public address is assigned to a specific device allowing the device tobe addressed directly by other devices on the Internet. Because thesepublic addresses on the Internet are in limited supply, devices andcomputers on the private network often use a router device, likeintegrated router 122, to share a single public address through entriesin Network Address Translation (NAT) table. The router makes an entry inthe NAT table for each communication channel opened between a device onthe private network and a device, server, or service on the Internet. Apacket sent from a device on the private network initially has a“source” address containing the private network address of the sendingdevice and a “destination” address corresponding to the public networkaddress of the server or service on the Internet. As packets pass fromwithin the private network through the router, the router replaces the“source” address with the public network address of the router and a“source port” that references the entry in the NAT table. The server onthe Internet receiving the packet uses the “source” address and “sourceport” to send packets back to the router on the private network which inturn forwards the packets to the proper device on the private networkdoing a corresponding lookup on an entry in the NAT table.

Entries in the NAT table allow both the computer device 124 and thethermostat 110 to establish individual communication channels with athermostat management system (not shown) located on a public networksuch as the Internet. In accordance with some embodiments, a thermostatmanagement account on the thermostat management system enables acomputer device 124 in enclosure 100 to remotely access thermostat 110.The thermostat management system passes information from the computerdevice 124 over the Internet and back to thermostat 110 provided thethermostat management account is associated with or paired withthermostat 110. Accordingly, data collected by thermostat 110 alsopasses from the private network associated with enclosure 100 throughintegrated router 122 and to the thermostat management system over thepublic network. Other computer devices not in enclosure 100 such asSmartphones, laptops and tablet computers (not shown in FIG. 1) may alsocontrol thermostat 110 provided they have access to the public networkwhere the thermostat management system and thermostat management accountmay be accessed. Further details on accessing the public network, suchas the Internet, and remotely accessing a thermostat like thermostat 110in accordance with embodiments of the present invention is described infurther detail later herein.

In some embodiments, thermostat 110 may wirelessly communicate withremote thermostat 112 over the private network or through an ad hocnetwork formed directly with remote thermostat 112. During communicationwith remote thermostat 112, thermostat 110 may gather informationremotely from the user and from the environment detectable by the remotethermostat 112. For example, remote thermostat 112 may wirelesslycommunicate with the thermostat 110 providing user input from the remotelocation of remote thermostat 112 or may be used to display informationto a user, or both. Like thermostat 110, embodiments of remotethermostat 112 may also include sensors to gather data related tooccupancy, temperature, light and other environmental conditions. In analternate embodiment, remote thermostat 112 may also be located outsideof the enclosure 100.

FIG. 2 is a schematic diagram of an HVAC system controlled using athermostat designed in accordance with embodiments of the presentinvention. HVAC system 120 provides heating, cooling, ventilation,and/or air handling for an enclosure 100, such as a single-family homedepicted in FIG. 1. System 120 depicts a forced air type heating andcooling system, although according to other embodiments, other types ofHVAC systems could be used such as radiant heat based systems, heat-pumpbased systems, and others.

In heating, heating coils or elements 242 within air handler 240 providea source of heat using electricity or gas via line 236. Cool air isdrawn from the enclosure via return air duct 246 through filter 270,using fan 238 and is heated through heating coils or elements 242. Theheated air flows back into the enclosure at one or more locations viasupply air duct system 252 and supply air registers such as register250. In cooling, an outside compressor 230 passes a gas such as Freonthrough a set of heat exchanger coils 244 to cool the gas. The gas thengoes through line 232 to the cooling coils 234 in the air handler 240where it expands, cools and cools the air being circulated via fan 238.A humidifier 254 may optionally be included in various embodiments thatreturns moisture to the air before it passes through duct system 252.Although not shown in FIG. 2, alternate embodiments of HVAC system 120may have other functionality such as venting air to and from theoutside, one or more dampers to control airflow within the duct system252 and an emergency heating unit. Overall operation of HVAC system 120is selectively actuated by control electronics 212 communicating withthermostat 110 over control wires 248.

Referring to FIG. 3A, a schematic block diagram provides an overview ofsome components inside a thermostat in accordance with embodiments ofthe present invention. Thermostat 308 is similar to thermostat 112 inFIG. 1 except that thermostat 308 also illustrates and highlightsselected internal components including a Wi-Fi module 312 and antenna, ahead unit processor 314 with associated memory 315, a backplateprocessor 316 with associated memory, and sensors 322 (e.g.,temperature, humidity, motion, ambient light, proximity). In oneembodiment, head unit processor 314 can be a Texas Instruments AM3703Sitara ARM microprocessor while backplate processor 316, which may bemore specifically referenced to as a “microcontroller”, can be a TexasInstruments MSP430F microcontroller. Further details regarding thephysical placement and configuration of the thermostat head unit,backplate, and other physical elements are described in the commonlyassigned U.S. Ser. No. 13/199,108, supra.

For some embodiments, the backplate processor 316 is a very low-powerdevice that, while having some computational capabilities, issubstantially less powerful than the head unit processor 314. Thebackplate processor 316 is coupled to, and responsible for polling on aregular basis, most or all of the sensors 322 including the temperatureand humidity sensors, motion sensors, ambient light sensors, andproximity sensors. For sensors 322 that may not be located on thebackplate hardware itself but rather are located in the head unit,ribbon cables or other electrical connections between the head unit andbackplate are provided for this purpose. Notably, there may be othersensors (not shown) for which the head unit processor 314 isresponsible, with one example being a ring rotation sensor that sensesthe user rotation of an outer ring of the thermostat. Each of the headunit processor 314 and backplate processor 316 is capable of enteringinto a “sleep” state, and then “waking up” to perform various tasks.

The backplate processor 316, which in some embodiments will have alow-power sleep state that corresponds simply to a lower clock speed,generally enters into and out of its sleep mode substantially more oftenthan does the more powerful head unit processor 314. The backplateprocessor 316 is capable of waking up the head unit processor 314 fromits sleep state. For one preferred embodiment directed to optimalbattery conservation, the head unit processor 314 is allowed to sleepwhen its operations are not being called for, while the backplateprocessor 316 performs polling of the sensors 322 on an ongoing basis,maintaining the sensor results in memory 317. The backplate processor316 will wake up the head unit processor 314 in the event that (i) thesensor data indicates that an HVAC operation may be called for, such asif the current temperature goes below a currently active heatingsetpoint, or (ii) the memory 317 gets full and the sensor data needs tobe transferred up to the head unit processor 314 for storage in thememory 315. The sensor data can then be pushed up to the cloud server(thermostat management server) during a subsequent active communicationsession between the cloud server and the head unit processor 314.

In the case of Wi-Fi module 312, one embodiment may be implemented usingMurata Wireless Solutions LBWA19XSLZ module, which is based on the TexasInstruments WL1270 chipset supporting the 802.11 b/g/n WLAN standard.Embodiments of the present invention configure and program Wi-Fi module312 to allow thermostat 308 to enter into a low power or “sleep” mode toconserve energy until one or several events occurs. For example, in someembodiments the Wi-Fi module 312 may leave this low power mode when auser physically operates thermostat 308, which in turn may also causeactivation of both head-unit processor 314 and backplate processor 316for controlling functions in head-unit and backplate portions ofthermostat 110.

It is also possible for Wi-Fi module 312 to wake from a low power modeat regular intervals in response to a beacon from wireless access point372. To conserve energy, Wi-Fi module 312 may briefly leave the lowpower mode to acknowledge the beacon as dictated by the appropriatewireless standard and then return to a low power mode without activatingthe processors or other components of thermostat 308 in FIG. 3A. In analternative embodiment, Wi-Fi module 312 may also respond to the beaconby awaking briefly and then activating backplate processor 316, headunit processor 314, or other portions of thermostat 308 to gather datathrough sensors 322 and store the results in a data log 326 with a timestamp, event type and corresponding data listed for future reference. Inaccordance with one embodiment, backplate processor 316 may collect datain data log 326 and store in memory 320 for a period of time or untilthe log reaches a maximum predetermined size. At that point, thebackplate processor 316 may wake head unit processor 314 to coordinatean upload of the data log 326 stored in memory 320 over a publicnetwork, such as the Internet, to cloud-based management server 516.Uploading data log 326 less frequently saves time and energy associatedwith more frequent transmission of individual records or log entries.

In yet another embodiment, Wi-Fi module 312 may selectively filter anincoming data packet to determine if the header is merely anacknowledgement packet (i.e., a keep-alive packet) or contains a payloadthat needs further processing. If the packet contains only a header andno payload, the Wi-Fi module 312 may be configured to either ignore thepacket or send a return acknowledgement to the thermostat managementsystem or other source of the packet received.

In further embodiments, Wi-Fi module 312 may be used to establishmultiple communication channels between thermostat 112 and a cloud-basedmanagement server as will be described and illustrated later in thisdisclosure. As previously described, thermostat 112 uses multiplecommunication channels to receive different types of data classifiedwith different levels of priority. In one embodiment, Wi-Fi module 312may be programmed to use one or more filters and a wake-on-LAN featureto then selectively ignore or discard data arriving over one or more ofthese communication channels. For example, low-priority data arrivingover a port on Wi-Fi module 312 may be discarded by disabling thecorresponding wake-on-LAN feature associated with the port. This allowsthe communication channel to continue to operate yet conserves batterypower by discarding or ignoring the low-priority packets.

Operation of the microprocessors 314, 316, Wi-Fi module 312, and otherelectronics may be powered by a rechargeable battery (not shown) locatedwithin the thermostat 110. In some embodiments, the battery is rechargeddirectly using 24 VAC power off a “C” wire drawn from the HVAC system oran AC-DC transformer coupled directly into the thermostat 110.Alternatively, one or more different types of energy harvesting may alsobe used to recharge the internal battery if these direct methods are notavailable as described, for example, in U.S. Ser. No. 13/034,678, supra,and U.S. Ser. No. 13/267,871, supra. Embodiments of the presentinvention communicate and operate the thermostat 110 in a manner thatpromotes efficient use of the battery while also keeping the thermostatoperating at a high level of performance and responsiveness controllingthe HVAC system. Some embodiments may use the battery-level charge andthe priority or relative importance of a communication to determine whena thermostat management system located on a public network such as theInternet may communicate with the thermostat 110. Further details on thecommunication methods and system used in accordance with theseembodiments are described in detail later herein.

Turning now to power harvesting methods and systems, FIG. 3B is a blockdiagram of some circuitry of a thermostat, according to someembodiments. Circuitry 300, according to some embodiments, is abackplate of a thermostat. A number of HVAC wires can be attached usingHVAC terminals 372. One example of which is the W1 terminal 374. Eachterminal is used to control an HVAC function. According to someembodiments, each of the wires from the terminals W1, W2, Y1, Y2, G,O/B, AUX and E is connected to separate isolated FET drives 370. Thecommon HVAC functions for each of the terminals are: W1 and W2 heating;Y1 and Y2 for cooling; G for fan; O/B for heatpumps; and E for emergencyheat. Note that although the circuitry 300 is able control 8 functionsusing the isolated FET drives 370, according to some embodiments, otherfunctions, or fewer functions can be controlled. For example circuitryfor a more simply equipped HVAC system may only have a single heating(W), and single cooling (Y) and a fan (G), in which case there wouldonly be three isolated FET drives 370. According to a preferredembodiment, 5 FET drives 370 are provided, namely heating (W), cooling(Y), fan (G), auxiliary (AUX) and compressor direction (O/B). Not shownare the circuit returns such as RH (return for heat) and RC (return forcooling). According to some embodiments the thermostat can control ahumidifier and/or de-humidifier. Further details relating to isolatedFET drives 370 are described in co-pending U.S. patent application Ser.No. 13/034,674, entitled “Thermostat Circuitry for Connection to HVACSystems,” supra, which is incorporated herein by reference.

The HVAC functions are controlled by the HVAC control general purposeinput/outputs (GPIOs) 322 within microcontroller (MCU) 320. MCU 320 is ageneral purpose microcontroller such as the MSP430 16-bit ultra-lowpower MCU available from Texas Instruments. MCU 320 communicates withthe head unit via Head Unit Interface 340. The head unit together withthe backplate make up the thermostat. The head unit has user interfacecapability such that it can display information to a user via an LCDdisplay and receive input from a user via buttons and/or touch screeninput devices. According to some embodiments, the head unit has networkcapabilities for communication to other devices either locally or overthe internet. Through such network capability, for example, thethermostat can send information and receive commands and setting from acomputer located elsewhere inside or outside of the enclosure. The MCUdetects whether the head unit is attached to the backplate via head unitdetect 338.

Clock 342 provides a low frequency clock signal to MCU 320, for example32.768 kHz. According to some embodiments there are two crystaloscillators, one for high frequency such as 16 MHz and one for the lowerfrequency. Power for MCU 320 is supplied at power input 344 at 3.0 V.Circuitry 336 provides wiring detection, battery measurement, and buckinput measurement. A temperature sensor 330 is provided, and accordingto some embodiments and a humidity sensor 332 are provided. According tosome embodiments, one or more other sensors 334 are provided such as:pressure, proximity (e.g. using infrared), ambient light, andpyroelectric infrared (PIR).

Power circuitry 350 is provided to supply power. According to someembodiments, when the thermostat is first turned on with insufficientbattery power, a bootstrap power system is provided. A high voltage lowdropout voltage regulator (LDO) 380 provides 3.0 volts of power for thebootstrap of the MCU 320. The bootstrap function can be disabled underMCU control but according to some embodiments the bootstrap function isleft enabled to provide a “safety net” if the head unit supply vanishesfor any reason. For example, if the head-unit includes the re-chargeablebattery 384 and is removed unexpectedly, the power would be lost and thebootstrap function would operate. The input to this Bootstrap LDO 380 isprovided by connectors and circuitry 368 that automatically selectspower from common 362 (highest priority), cool 366 (lower priority); orheat (lowest priority) 364.

In normal operation, a 3.0 volt primary LDO 382 powers the backplatecircuitry and itself is powered by VCC Main. According to someembodiments, high voltage buck 360 is provided as a second supply in thebackplate. The input to this supply is the circuitry 368. According tosome embodiments, the high voltage buck 380 can supply a maximum of 100mA at 4.5 v. According to some embodiments, the VCC main and the PrimaryLDO 382 can be powered by a rechargeable battery (shown in FIG. 7) incases where there is no alternative power source (such as the highvoltage buck or USB power, for example).

FIGS. 4A-C schematically illustrate the use of auto-switching connectorsbeing used to automatically select a source for power harvesting,according to some embodiments. The connectors 362, 364, and 366 areconnectors as shown in FIG. 3B. For further details regarding preferredautomatically switching connectors, see co-pending U.S. patentapplication Ser. No. 13/034,666, entitled “Thermostat Wiring Connector”filed on even date herewith and incorporated herein by reference. Theconnector 362 is used for connection to an HVAC “C” (common) wire andincludes two switched pairs of normally closed secondary conductors 410and 412. The connector 366 is used for connection to an HVAC “Y”(cooling) wire and includes one switched pair of normally closedsecondary conductors 454. The connector 364 is used for connection to anHVAC “W” (heating) wire. Note that although not shown in FIGS. 4A-C, oneor more additional pairs of switched secondary conductors can beprovided with any of the connectors 362, 366 and 365, such as could beused for the purpose of electronically detecting the presence of an HVACsystem wire to the connector. Power harvesting circuitry 460 is used tosupply power to the thermostat and is also connected to the Rc wire 462(or according to other embodiment the Rh wire). For example, the powerharvesting circuitry 460 can include the HV buck 360 and Bootstrap LDO380 as shown in and described with respect to FIGS. 3 and 6A-B.

FIG. 4A shows the case of the switches 454, 410 and 412 when no C wireand no Y wire is attached. In this case all of the switches 454, 410 and412 are closed and the power harvesting circuitry 460 is connected atinput 464 with the W wire via circuit paths 420, 422 and 426. FIG. 4Bshows the case of the switches 454, 410 and 412 when no C wire isattached but there is a Y wire attached. In this case switches 410 and412 are closed but switch 454 is opened due to the presence of the Ywire. In this case the power harvesting circuitry 460 is connected atinput 464 with the Y wire via circuit paths 424 and 428. FIG. 4C showsthe case of the switches 454, 410, and 412, when both C and Y wires areattached. In this case all the switches 454, 410 and 412 are open andthe power harvesting circuitry 460 is connected at input 464 with the Cwire via circuit path 430. Note that the case of a connection of C and Wwires and no Y wire is not shown but that in this case the W wire wouldnot be connected to circuitry 420 since switch 410 would be open. Thus,through the use of circuitry and the connectors shown, the powerharvesting circuitry is automatically switched so as to use connectionsto C, Y and W wires in decreasing order of priority. Preferably, the Cwire is the highest priority as this ordinarily provides the best powersource, if available. Note that according to some embodiments, the Y andW priorities are reversed to make W higher priority than Y.

FIG. 5 is a schematic of a half-bridge sense circuit, according to someembodiments. Circuit 500 provides voltage sensing, clipped to 3.0 volts,for presence detection and current sensing. At inputs 502, 504 and 506are the 24 VAC waveforms from three of the HVAC circuits. In the caseshown in FIG. 5, inputs 502, 504 and 506 are for HVAC W1, HVAC Y1 andHVAC G, respectively. The sense input bias buffer 550 is provided asshown. Note that a voltage divider is used in each case that takes thevoltage from 24 volts to approximately 4 volts. Clamp diodes 520 a, 520b and 520 c ensure that the voltage goes no higher or lower than therange of the microcontroller 320 (shown in FIG. 3B). The Sense outputs530, 532 and 534 are connected to the microcontroller 320 so that themicrocontroller 320 can sense the presence of a signal on the HVAClines. The circuits are repeated for the other HVAC lines so that themicrocontroller can detect signals on any of the HVAC lines.

FIGS. 6A-B are schematics showing the high voltage buck, bootstrap LDOand battery LDO power circuitry, according to some embodiments. FIG. 6Ashows the input 464 from the connector selected power, which correspondsto input 464 to power circuitry 460 in FIG. 4. The diodes 632 are usedto rectify the AC power signal from the HVAC power transformer wire thatis selected by the connector circuitry shown in FIG. 4. When thethermostat is installed in a building having two HVAC powertransformers, such as may be the case when an existing HVAC heating-onlysystem is upgraded to add an HVAC cooling system. In such cases, thereare two power wires from the HVAC system, often called “Rh” the powerwire directly from the heating system transformer, and “Rc” the powerwire directly from the cooling transformer. Input 462 is from a terminalconnected to the Rc wire. According to some embodiments, the Rc and Rhterminals are switched using automatic switching or other jumperlessdesign, as shown and described in co-pending U.S. patent applicationSer. No. 13/034,674, entitled “Thermostat Circuitry for Connection toHVAC Systems,” filed Feb. 24, 2011 and incorporated herein by reference.

Rectified input 624 is input to the high voltage buck circuit 610,according to some embodiments. In buck circuit 610, which corresponds tohigh voltage buck 360 in FIG. 3B, the voltage on the input capacitors612, 614 and 616 of high voltage buck 610 can be measured by the MCU 320(of FIG. 3B) at node 620, allowing the MCU to momentarily open the W1 orY1 contacts during an “enabled” or “on” phase in order to recharge thebuck input capacitors 612, 614 and 616 and continue power harvesting.According to some embodiments, the same HVAC circuit (e.g. heating orcooling) is used for power harvesting, whether or not there is more thanone HVAC function in the system. According to some other embodiments,when the thermostat is used with an HVAC system having two circuits(e.g. heating and cooling), the system will harvest power from thenon-activated circuit. In cases where a common wire is available fromthe HVAC power transformer, the system preferably does not power harvestat all from the heating and cooling circuits. According to someembodiments, the step down converter 630 is a high efficiency, highvoltage 100 mA synchronous step-down converter such as the LTC3631 fromLinear Technology. According to some embodiments, inductor 642 is a100uH power inductor such as the MOS6020 from Coilcraft. According tosome embodiments, one or more other types of elements in addition to orinstead of input capacitors 612, 614 and 616 are used to storeelectrical energy during power harvesting when the HVAC function isactive (or “on”). For example, magnetic elements such as inductorsand/or transformers can be used.

In order to control the HVAC functions, the HVAC function wire isshorted to the return or power wire. For example, in the case ofheating, the W wire is shorted to the Rh (or R or Rc depending on theconfiguration). In the case of cooling the Y wire is shorted to the Rc(or R or Rh depending on the configuration). By shorting these twowires, the 24 VAC transformer is placed in series with a relay thatcontrols the HVAC function. However, for power harvesting, a problem isthat when these wires are shorted, there is no voltage across them, andwhen open, there is no current flow. Since power equals voltagemultiplied by current, if either quantity is zero the power that can beextracted is zero. According to some embodiments, the power harvestingcircuitry allows power to be taken from the two wires in both the statesof HVAC—the HVAC “on” and the HVAC “off”.

In the HVAC “off” state, some energy can be harvested from these twowires by taking less energy than would cause the of the relay to turnon, which would cause the HVAC function to erroneously turn on. Based ontesting, it has been found that HVAC functions generally do not turn onwhen (0.040 A*4.5V)=0.180 watts is extracted at the output. So after theinput diodes, capacitors, and switching regulator, this allows us totake 40 mA at 4.5 volts from these wires without turning on the HVACsystem.

In the HVAC “on” state, the two wires must be connected together toallow current to flow, which turns on the HVAC relay. This, however,shorts out the input supply, so our system does not get any power whenthe HVAC “on” switch is closed. To get around this problem, the voltageis monitored on the capacitors 612, 614 and 616 at the input switchingpower supply node 620. When the voltage on these capacitors “C_(in)”drops close to the point at which the switching power supply would “Dropout” and lose output regulation, for example at about +8 Volts, the HVAC“on” switch is turned off and C_(in) is charged. During the time thatC_(in) is charging, current is still flowing in the HVAC relay, so theHVAC relay stays on. When the C_(in) capacitor voltages increases someamount, for example about +16 Volts, the HVAC “on” switch is closedagain, C_(in) begins to discharge while it feeds the switchingregulator, and current continues to flow in the HVAC relay. Note thatC_(in) is not allowed to discharge back to the HVAC “on” switch due toinput diodes 632. When the voltage on C_(in) drops to about +8 Volts theHVAC “on” switch is turned off and the process repeats. This continuesuntil the system tells the HVAC “on” switch to go off because HVAC is nolonger needed. According to some embodiments, the ability of the HVAC“on” switch to turn on and off relatively quickly is provided bycircuitry 450 as shown in and described with respect to FIG. 4 ofco-pending U.S. patent application Ser. No. 13/034,674, entitled“Thermostat Circuitry for Connection to HVAC Systems,” supra, which isincorporated herein by reference.

According to some embodiments, one or more alternative power harvestingtechniques are used. For example, rather than having the HVAC “on”switch turn on when the voltage on C_(in) reaches a certain point, itthe system might turn off the “HVAC “on” switch for a predeterminedperiod of time instead. According to some embodiments, power harvestingis enhanced by synchronizing the power harvesting with the AC currentwaveform.

FIG. 6B is a schematic of high voltage low dropout voltage regulatorsused to provide bootstrap power and battery, according to someembodiments. The bootstrap LDO circuitry 680, and battery LDO circuitrycorrespond to the bootstrap LDO 380 and battery LDO 382 in FIG. 3respectively. Rectified input 624 is input to bootstrap circuit 680.According to some embodiments, regulator 670 is low-dropout linearregulator such as the TPS79801 from Texas Instruments. The output power690 is provided to the backplate at 3.0V. The bootstrap disable signal680 can be used to disable the bootstrap power unit, as shown. The input660 comes from VCC main, which can be, for example, from therechargeable battery. According to some embodiments, the low dropoutregulator 662 is a low quiescent current device designed forpower-sensitive applications such as the TLV70030 from TexasInstruments.

FIG. 6C shows a battery charging circuit 675 and a rechargeable battery650, according to some embodiments. The charger 673 is used to chargethe lithium-ion battery 650. In general, li-ion battery capacity dependson what voltage the battery is charged to, and the cycle life depends onthe charged voltage, how fast the battery is charged and the temperatureduring which the battery is charged. Ordinarily, Li-ion batteries arecharged at about 4.2V. In some cases the charging voltage is even higherin an attempt to gain greater capacity, but at the expense of decreasedcycle life. However, in the case of the rechargeable battery 650 for usewith a wall-mounted thermostat, a greater cycle life is preferred overcapacity. High capacity is generally not needed since charging power isavailable via the power harvesting circuitry, and greater cycle life ispreferred since user replacement may be difficult or unavailable. Thus,according to some embodiments, a low charging speed, low final floatvoltage and reduced charging temperature range is preferred. Accordingto some embodiments, a final float voltage of between 3.9V and 4.1V isused. According to some embodiments a final float voltage of less than4.0V is used, such as 3.95V. According to some embodiments, the ratio ofcharge current to total capacity “C” is also controlled, such ascharging the battery to 0.2C (0.2 times the rated capacity) to providebetter cycle life than a higher ratio. According to some embodiments,using a lower charging current aids in avoiding unintended tripping ofthe HVAC relay.

According to some embodiments, charger 673 is a USB power manager andli-ion battery charger such as the LTC4085-3 from Linear Technology.Backplate voltage 671 is input to charger 673. The circuitry 672 is usedto select the charging current. In particular the value of resistor 674(24.9 k) in parallel with resistor 634 (16.9 k) in combination with theinputs Double Current 638 and High Power 628 are used to select thecharging current. If High Power 628 and Double Current 638 are both setto 0, then the charging current is 8.0 mA; if the High Power 628 is setto 0 and Double Current 638 is set to 1, then the charging current is19.9 mA; if the High Power 628 is set to 1 and Double Current 638 is setto 0, then the charging current is 40.1 mA; and if the High Power 628and Double Current 638 are both set to 1, then the charging current is99.3 mA. Resistor 636 is used to set the default charge current. In thecase shown, a 220 k resistor set the default charge current to 227 mA.According to some embodiments, a charge temperature range of 0-44degrees C. is set via the Thermistor Monitoring Circuits.

According to some embodiments, the thermostat is capable of beingpowered by a USB power supply. This could be supplied by a user, forexample, by attaching the thermostat via a USB cable to a computer oranother USB power supply. In cases where USB power supply is available,it is selected as the preferred power source for the thermostat and canbe used to recharge the rechargeable battery. According to someembodiments, a charge current of about 227 mA is used when a USB supplysource is available; a charge current of about 100 mA is used when anHVAC common wire is present; and a charge current of between about 20-40mA is used when power is harvested from an HVAC heating and/or coolingcircuit.

FIG. 7 illustrates an exploded perspective view of a thermostat or VSCU(versatile sensing and control unit) 700 and an HVAC-coupling wall dock702 according to an embodiment. For first-time customers who are goingto be replacing their old thermostat, the VSCU unit 700 is provided incombination with HVAC-coupling wall dock 702. The HVAC-coupling walldock 702 comprises mechanical hardware for attaching to the wall andelectrical terminals for connecting to the HVAC wiring 298 that will beextending out of the wall in a disconnected state when the oldthermostat is removed. The HVAC-coupling wall dock 702 is configuredwith an electrical connector 704 that mates to a counterpart electricalconnector 705 in the VSCU 700.

For the initial installation process, the customer (or their handyman,or an HVAC professional, etc.) first installs the HVAC-coupling walldock 702, including all of the necessary mechanical connections to thewall and HVAC wiring connections to the HVAC wiring 298. Once theHVAC-coupling wall dock 702 is installed, which represents the “hardwork” of the installation process, the next task is relatively easy,which is simply to slide the VSCU unit 700 thereover to mate theelectrical connectors 704/705. Preferably, the components are configuredsuch that the HVAC-connecting wall dock 702 is entirely hiddenunderneath and inside the VSCU unit 700, such that only the visuallyappealing VSCU unit 700 is visible.

For one embodiment, the HVAC-connecting wall dock 702 is a relatively“bare bones” device having the sole essential function of facilitatingelectrical connectivity between the HVAC wiring 298 and the VSCU unit700. For another embodiment, the HVAC-coupling wall dock 702 is equippedto perform and/or facilitate, in either a duplicative sense and/or aprimary sense without limitation, one or more of the functionalitiesattributed to the VSCU unit 700 in the instant disclosure, using a setof electrical, mechanical, and/or electromechanical components 706. Oneparticularly useful functionality is for the components 706 to includepower-extraction circuitry for judiciously extracting usable power fromthe HVAC wiring 298, at least one of which will be carrying a 24-volt ACsignals in accordance with common HVAC wiring practice. Thepower-extraction circuitry converts the 24-volt AC signal into DC power(such as at 5 VDC, 3.3 VDC, etc.) that is usable by the processingcircuitry and display components of the main unit 701.

The division and/or duplication of functionality between the VSCU unit700 and the HVAC-coupling wall dock 702 can be provided in manydifferent ways without departing from the scope of the presentteachings. For another embodiment, the components 706 of theHVAC-coupling wall dock 702 can include one or more sensing devices,such as an acoustic sensor, for complementing the sensors provided onthe sensor ring 104 of the VSCU unit 700. For another embodiment, thecomponents 706 can include wireless communication circuitry compatiblewith one or more wireless communication protocols, such as the Wi-Fiand/or ZigBee protocols. For another embodiment, the components 706 caninclude external AC or DC power connectors. For another embodiment, thecomponents 706 can include wired data communications jacks, such as anRJ45 Ethernet jack, an RJ11 telephone jack, or a USB connector.

The docking capability of the VSCU unit 700 according to the embodimentof FIG. 7 provides many advantages and opportunities in both atechnology sense and a business sense. Because the VSCU unit 700 can beeasily removed and replaced by even the most non-technically-savvycustomer, many upgrading and upselling opportunities are provided. Forexample, many different versions of the VSCU unit 700 can be separatelysold, the different versions having different colors, styles, themes,and so forth. Upgrading to a new VSCU unit 700 having more advancedcapabilities becomes a very easy task, and so the customer will bereadily able to take advantage of the newest display technology, sensortechnology, more memory, and so forth as the technology improves overtime.

Provided in accordance with one or more embodiments related to thedocking capability shown in FIG. 7 are further devices and features thatadvantageously promote expandability of the number of sensing andcontrol nodes that can be provided throughout the home. For oneembodiment, a tabletop docking station (not shown) is provided that iscapable of docking to a second instance of the VSCU unit 700, which istermed herein an auxiliary VSCU unit (not shown). The tabletop dockingstation and the auxiliary VSCU unit can be separately purchased by theuser, either at the same time they purchase their original VSCU unit700, or at a later time. The tabletop docking station is similar infunctionality to the HVAC-coupling wall dock 702, except that it doesnot require connection to the HVAC wiring 298 and is convenientlypowered by a standard wall outlet. For another embodiment, instead ofbeing identical to the original VSCU unit 700, the auxiliary VSCU unitcan be a differently labeled and/or differently abled version thereof.

As used herein, the term “primary VSCU unit” refers to one that iselectrically connected to actuate an HVAC system in whole or in part,which would necessarily include the first VSCU unit purchased for anyhome, while the term “auxiliary VSCU unit” refers to one or moreadditional VSCU units not electrically connected to actuate an HVACsystem in whole or in part. An auxiliary VSCU unit, when docked, willautomatically detect the primary VSCU unit and will automatically bedetected by the primary VSCU unit, such as by Wi-Fi or ZigBee wirelesscommunication. Although the primary VSCU unit will remain the soleprovider of electrical actuation signals to the HVAC system, the twoVSCU units will otherwise cooperate in unison for improved controlheating and cooling control functionality, such improvement beingenabled by virtue of the added multi-sensing functionality provided bythe auxiliary VSCU unit, as well as by virtue of the additionalprocessing power provided to accommodate more powerful and precisecontrol algorithms. Because the auxiliary VSCU unit can accept usercontrol inputs just like the primary VSCU unit, user convenience is alsoenhanced. Thus, for example, where the tabletop docking station and theauxiliary VSCU unit are placed on a nightstand next to the user's bed,the user is not required to get up and walk to the location of theprimary VSCU unit if they wish to manipulate the temperature set point,view their energy usage, or otherwise interact with the system.

A variety of different VSCU-compatible docking stations are within thescope of the present teachings. For example, in another embodiment thereis provided an auxiliary wall dock (not shown) that allows an auxiliaryVSCU unit to be mounted on a wall. The auxiliary wall dock is similar infunctionality to the tabletop docking station in that it does notprovide HVAC wiring connections, but does serve as a physical mountingpoint and provides electrical power derived from a standard wall outlet.

For one embodiment, all VSCU units sold by the manufacturer areidentical in their core functionality, each being able to serve aseither a primary VSCU unit or auxiliary VSCU unit as the case requires,although the different VSCU units may have different colors, ornamentaldesigns, memory capacities, and so forth. For this embodiment, the useris advantageously able, if they desire, to interchange the positions oftheir VSCU units by simple removal of each one from its existing dockingstation and placement into a different docking station. Among otheradvantages, there is an environmentally, technically, and commerciallyappealing ability for the customer to upgrade to the newest, latest VSCUdesigns and technologies without the need to throw away the existingVSCU unit. For example, a customer with a single VSCU unit (which isnecessarily serving as a primary VSCU unit) may be getting tired of itscolor or its TFT display, and may be attracted to a newly released VSCUunit with a different color and a sleek new OLED display. For this case,in addition to buying the newly released VSCU, the customer can buy atabletop docking station to put on their nightstand. The customer canthen insert their new VSCU unit into the existing HVAC-coupling walldock, and then take their old VSCU unit and insert it into the tabletopdocking station. Advantageously, in addition to avoiding thewastefulness of discarding the old VSCU unit, there is now a newauxiliary VSCU unit at the bedside that not only provides increasedcomfort and convenience, but that also promotes increased energyefficiency by virtue of the additional multi-sensor information andprocessing power provided.

For other embodiments, different VSCU units sold by the manufacturer canhave different functionalities in terms of their ability to serve asprimary versus auxiliary VSCU units. This may be advantageous from apricing perspective, since the hardware cost of an auxiliary-only VSCUunit may be substantially less than that of a dual-capabilityprimary/auxiliary VSCU unit. In other embodiments there is provideddistinct docking station capability for primary versus auxiliary VSCUunits, with primary VSCU units using one kind of docking connectionsystem and auxiliary VSCU units using a different kind of dockingconnection system. In still other embodiments there is provided thedocking station capability of FIG. 7 for primary VSCU units, but nodocking station capability for auxiliary VSCU units, wherein auxiliaryVSCU units are simply provided in monolithic form as dedicated auxiliarytabletop VSCU units, dedicated auxiliary wall-mounted VSCU units, and soforth. One advantage of providing an auxiliary VSCU unit, such as atabletop VSCU unit, without a docking functionality would be itssimplicity and non-intimidating nature for users, since the user wouldsimply be required to place it on a table (their nightstand, forexample) and just plug it in, just as easily as they would a clockradio.

In still other embodiments, all VSCU units are provided as non-dockingtypes, but are interchangeable in their abilities as primary andauxiliary VSCU units. In still other embodiments, all VSCU units areprovided as non-docking types and are non-interchangeable in theirprimary versus auxiliary abilities, that is, there is a first set ofVSCU units that can only serve as primary VSCU units and a second set ofVSCU units that can only serve as auxiliary VSCU units. For embodimentsin which primary VSCU units are provided as non-docking types, theirphysical architecture may still be separable into two components for thepurpose of streamlining the installation process, with one componentbeing similar to the HVAC-coupling wall dock 702 of FIG. 7 and thesecond component being the main unit as shown in FIG. 7, except that theassembly is not intended for docking-style user separability afterinstallation is complete. For convenience of description hereinbelow andso as not to unnecessarily limit the scope of the present teachings, theclassification of one or more described VSCU units as being of (i) anon-docking type versus a docking type, and/or (ii) a primary typeversus an auxiliary type, may not be specified, in which case VSCU unitsof any of these classifications may be used with such embodiments, or inwhich case such classification will readily inferable by the skilledartisan from the context of the description.

FIG. 8A illustrates a conceptual diagram of an HVAC-coupling wall dock702′ with particular reference to a set of input wiring ports 851thereof, and which represents a first version of the HVAC-coupling walldock 702 of FIG. 7 that is manufactured and sold in a “simple” or “DIY(do-it-yourself)” product package in conjunction with the VSCU unit 700.The input wiring ports 851 of the HVAC-coupling wall dock 702′ arejudiciously limited in number and selection to represent a business andtechnical compromise between (i) providing enough control signal inputsto meet the needs of a reasonably large number of HVAC systems in areasonably large number of households, while also (ii) not intimidatingor overwhelming the do-it-yourself customer with an overly complex arrayof connection points. For one embodiment, the judicious selection ofinput wiring ports 851 consists of the following set: Rh (24 VAC heatingcall switch power); Rc (24 VAC cooling call switch power); W (heatingcall); Y (cooling call); G (fan); and O/B (heat pump).

The HVAC-coupling wall dock 702′ is configured and designed inconjunction with the VSCU unit 700, including both hardware aspects andprogramming aspects, to provide a DIY installation process that issimple, non-intimidating, and perhaps even fun for many DIY installers,and that further provides an appreciable degree of foolproofingcapability for protecting the HVAC system from damage and for ensuringthat the correct signals are going to the correct equipment. For oneembodiment, the HVAC-coupling wall dock 702′ is equipped with a smallmechanical detection switch (not shown) for each distinct input port,such that the insertion of a wire (and, of course, the non-insertion ofa wire) is automatically detected and a corresponding indication signalis provided to the VSCU 100 upon initial docking. In this way, the VSCU100 has knowledge for each individual input port whether a wire has, orhas not been, inserted into that port. Preferably, the VSCU unit 700 isalso provided with electrical sensors (e.g., voltmeter, ammeter, andohmmeter) corresponding to each of the input wiring ports 851. The VSCU100 is thereby enabled, by suitable programming, to perform somefundamental “sanity checks” at initial installation. By way of example,if there is no input wire at either the Rc or Rh terminal, or if thereis no AC voltage sensed at either of these terminals, furtherinitialization activity can be immediately halted, and the user notifiedon the circular display monitor 102, because there is either no power atall or the user has inserted the Rc and/or Rh wires into the wrongterminal. By way of further example, if there is alive voltage on theorder of 24 VAC detected at any of the W, Y, and G terminals, then itcan be concluded that the user has placed the Rc and/or Rh wire in thewrong place, and appropriate installation halting and user notificationcan be made.

One particularly advantageous feature from a safety and equipmentpreservation perspective provided according to one embodiment relates toautomated opening versus automated shunting of the Rc and Rh terminalsby the VSCU unit 700. In many common home installations, instead ofthere being separate wires provided for Rc (24 VAC heating call switchpower) and Rh (24 VAC cooling call switch power), there is only a single24 VAC call switch power lead provided. This single 24 VAC lead, whichmight be labeled R, V, Rh, or Rc depending on the unique history andgeographical location of the home, provides the call switch power forboth heating and cooling. For such cases, it is electrically necessaryfor any thermostat to have its Rc and Rh input ports shunted together sothat the power from that single lead can be respectively accessed by theheating and cooling call switches. However, in many other common homeinstallations, there are separate 24 VAC wires provided for Rc and Rhrunning from separate transformers and, when so provided, it isimportant not to shunt them together to avoid equipment damage. Thesesituations are resolved historically by (i) the professional installerexamining the HVAC system and ensuring that a shunting lead (orequivalent DIP switch setting) is properly installed or not installed asappropriate, and/or (ii) the historical presence on most thermostats ofa discrete user-toggled mechanical or electromechanical switch (e.g.,HEAT-OFF-COOL) to ensure that heating and cooling are neversimultaneously activated. Notably, it is desired to omit any discretemechanical HEAT-OFF-COOL in most embodiments and to eliminate the needfor a professional installer for the instant DIY product versionenvironment. Advantageously, according to an embodiment, the VSCU 100 isadvantageously equipped and programmed to (i) automatically test theinserted wiring to classify the user's HVAC system into one of the abovetwo types (i.e., single call power lead versus dual call power leads),(ii) to automatically ensure that the Rc and Rh input ports remainelectrically segregated if the if the user's HVAC system is determinedto be of the dual call power lead type, and (iii) to automatically shuntthe Rc and Rh input ports together if the user's HVAC system isdetermined to be of the single call power lead type. The automatictesting can comprise, without limitation, electrical sensing such asthat provided by voltmeter, ammeters, ohmmeters, and reactance-sensingcircuitry, as well as functional detection as described further below.

Also provided at installation time according to an embodiment, which isparticularly useful and advantageous in the DIY scenario, is automatedfunctional testing of the HVAC system by the VSCU unit 700 based on thewiring insertions made by the installer as detected by the smallmechanical detection switches at each distinct input port. Thus, forexample, where an insertion into the W (heating call) input port ismechanically sensed at initial startup, the VSCU unit 700 actuates thefurnace (by coupling W to Rh) and then automatically monitors thetemperature over a predetermined period, such as ten minutes. If thetemperature is found to be rising over that predetermined period, thenit is determined that the W (heating call) lead has been properlyconnected to the W (heating call) input port. However, if thetemperature is found to be falling over that predetermined period, thenit is determined that Y (cooling call) lead has likely been erroneouslyconnected to the W (heating call) input port. For one embodiment, whensuch error is detected, the system is shut down and the user is notifiedand advised of the error on the circular display monitor 102. Foranother embodiment, when such error is detected, the VSCU unit 700automatically reassigns the W (heating call) input port as a Y (coolingcall) input port to automatically correct the error. Similarly,according to an embodiment, where the Y (cooling call) lead ismechanically sensed at initial startup, the VSCU unit 700 actuates theair conditioner (by coupling Y to Rc) and then automatically monitorsthe temperature, validating the Y connection if the temperature issensed to be falling and invalidating the Y connection (and, optionally,automatically correcting the error by reassigning the Y input port as aW input port) if the temperature is sensed to be rising. In view of thepresent disclosure, the determination and incorporation of otherautomated functional tests into the above-described method for otherHVAC functionality would be achievable by the skilled artisan and arewithin the scope of the present teachings. By way of example, for oneembodiment there can be a statistical study done on the electrical noisepatterns associated with the different control wires and a unique orpartially unique “noise fingerprint” associated with the differentwires, and then the VSCU unit 700 can automatically sense the noise oneach of the existing control wires to assist in the automated testingand verification process.

Also provided at installation time according to an embodiment, which islikewise particularly advantageous in the DIY scenario, is automateddetermination of the homeowner's pre-existing heat pump wiringconvention when an insertion onto the O/B (heat pump) input port ismechanically sensed at initial startup. Depending on a combination ofseveral factors such as the history of the home, the geographical regionof the home, and the particular manufacturer and installation year ofthe home's heat pump, there may be a different heat pump signalconvention used with respect to the direction of operation (heating orcooling) of the heat pump. According to an embodiment, the VSCU unit 700automatically and systematically applies, for each of a plurality ofpreselected candidate heat pump actuation signal conventions, a coolingactuation command and a heating actuation command, each actuationcommand being followed by a predetermined time period over which thetemperature change is sensed. If the cooling command according to thepresently selected candidate convention is followed by a sensed periodof falling temperature, and the heating command according to thepresently selected candidate convention is followed by a sensed periodof rising temperature, then the presently selected candidate conventionis determined to be the actual heat pump signal convention for thathome. If, on the other hand, the cooling command was not followed by asensed period of cooling and/or the heating command was not followed bya sensed period of heating, then the presently selected candidateconvention is discarded and the VSCU unit 700 repeats the process forthe next candidate heat pump actuation signal convention. For oneexample, a first candidate heat pump actuation signal convention is (a)for cooling, leave O/B open and connect Y to Rc, and (b) for heating,connect O/B to Rh, while a second candidate heat pump actuation signalconvention is (a) for cooling, connect O/B to Rc, and (b) for heating,leave O/B open and connect W to Rh. In view of the present disclosure,the determination and incorporation of other candidate heat pumpactuation signal conventions into the above-described method would beachievable by the skilled artisan and are within the scope of thepresent teachings.

FIG. 8B illustrates a conceptual diagram of an HVAC-coupling wall dock702″ with particular reference to a set of input wiring ports 861thereof, and which represents a second version of the HVAC-coupling walldock 702 of FIG. 7 that is manufactured and sold in a “professional”product package in conjunction with the VSCU unit 700. The professionalproduct package is preferably manufactured and marketed withprofessional installation in mind, such as by direct marketing to HVACservice companies, general contractors involved in the construction ofnew homes, or to homeowners having more complex HVAC systems with arecommendation for professional installation. The input wiring ports 861of the HVAC-coupling wall dock 702″ are selected to be sufficient toaccommodate both simple and complex HVAC systems alike. For oneembodiment, the input wiring ports 861 include the following set: Rh (24VAC heating call switch power); Rc (24 VAC cooling call switch power);W1 (first stage heating call); W2 (second stage heating call); Y1 (firststage cooling call); Y2 (second stage cooling call); G (fan); O/B (heatpump); AUX (auxiliary device call); E (emergency heating call); HUM(humidifier call); and DEHUM (dehumidifier call). For one embodiment,even though professional installation is contemplated, the HVAC-couplingwall dock 702″ is nevertheless provided with small mechanical detectionswitches (not shown) at the respective input wiring ports for wireinsertion sensing, and the VSCU unit 700 is provided with one or more ofthe various automated testing and automated configuration capabilitiesassociated with the DIY package described above, which may be useful forsome professional installers and/or more technically savvydo-it-yourselfers confident enough to perform the professional-modelinstallation for their more advanced HVAC systems.

FIGS. 9A-9B illustrate a thermostat 900 having a user-friendlyinterface, according to some embodiments. The term “thermostat” is usedhereinbelow to represent a particular type of VSCU unit (VersatileSensing and Control) that is particularly applicable for HVAC control inan enclosure. Although “thermostat” and “VSCU unit” may be seen asgenerally interchangeable for the contexts of HVAC control of anenclosure, it is within the scope of the present teachings for each ofthe embodiments hereinabove and hereinbelow to be applied to VSCU unitshaving control functionality over measurable characteristics other thantemperature (e.g., pressure, flow rate, height, position, velocity,acceleration, capacity, power, loudness, brightness) for any of avariety of different control systems involving the governance of one ormore measurable characteristics of one or more physical systems, and/orthe governance of other energy or resource consuming systems such aswater usage systems, air usage systems, systems involving the usage ofother natural resources, and systems involving the usage of variousother forms of energy. Unlike many prior art thermostats, thermostat 900preferably has a sleek, simple, uncluttered and elegant design that doesnot detract from home decoration, and indeed can serve as a visuallypleasing centerpiece for the immediate location in which it isinstalled. Moreover, user interaction with thermostat 900 is facilitatedand greatly enhanced over known conventional thermostats by the designof thermostat 900. The thermostat 900 includes control circuitry and iselectrically connected to an HVAC system, such as is shown withthermostat 110 in FIGS. 1 and 2. Thermostat 900 is wall mounted, iscircular in shape, and has an outer rotatable ring 912 for receivinguser input. Thermostat 900 is circular in shape in that it appears as agenerally disk-like circular object when mounted on the wall. Thermostat900 has a large front face lying inside the outer ring 912. According tosome embodiments, thermostat 900 is approximately 80 mm in diameter. Theouter rotatable ring 912 allows the user to make adjustments, such asselecting a new target temperature. For example, by rotating the outerring 912 clockwise, the target temperature can be increased, and byrotating the outer ring 912 counter-clockwise, the target temperaturecan be decreased. The front face of the thermostat 900 comprises a clearcover 914 that according to some embodiments is polycarbonate, and ametallic portion 924 preferably having a number of slots formed thereinas shown. According to some embodiments, the surface of cover 914 andmetallic portion 924 form a common outward arc or spherical shape gentlyarcing outward, and this gentle arcing shape is continued by the outerring 912.

Although being formed from a single lens-like piece of material such aspolycarbonate, the cover 914 has two different regions or portionsincluding an outer portion 914 o and a central portion 914 i. Accordingto some embodiments, the cover 914 is painted or smoked around the outerportion 914 o, but leaves the central portion 914 i visibly clear so asto facilitate viewing of an electronic display 916 disposedthereunderneath. According to some embodiments, the curved cover 914acts as a lens that tends to magnify the information being displayed inelectronic display 916 to users. According to some embodiments thecentral electronic display 916 is a dot-matrix layout (individuallyaddressable) such that arbitrary shapes can be generated, rather thanbeing a segmented layout. According to some embodiments, a combinationof dot-matrix layout and segmented layout is employed. According to someembodiments, central display 916 is a backlit color liquid crystaldisplay (LCD). An example of information displayed on the electronicdisplay 916 is illustrated in FIG. 9A, and includes central numerals 920that are representative of a current setpoint temperature. According tosome embodiments, metallic portion 924 has number of slot-like openingsso as to facilitate the use of a passive infrared motion sensor 930mounted therebeneath. The metallic portion 924 can alternatively betermed a metallic front grille portion. Further description of themetallic portion/front grille portion is provided in the commonlyassigned U.S. Ser. No. 13/199,108, supra. The thermostat 900 ispreferably constructed such that the electronic display 916 is at afixed orientation and does not rotate with the outer ring 912, so thatthe electronic display 916 remains easily read by the user. For someembodiments, the cover 914 and metallic portion 924 also remain at afixed orientation and do not rotate with the outer ring 912. Accordingto one embodiment in which the diameter of the thermostat 900 is about80 mm, the diameter of the electronic display 916 is about 45 mm.According to some embodiments an LED indicator 980 is positioned beneathportion 924 to act as a low-power-consuming indicator of certain statusconditions. For, example the LED indicator 980 can be used to displayblinking red when a rechargeable battery of the thermostat (see FIG. 4A,infra) is very low and is being recharged. More generally, the LEDindicator 980 can be used for communicating one or more status codes orerror codes by virtue of red color, green color, various combinations ofred and green, various different blinking rates, and so forth, which canbe useful for troubleshooting purposes.

Motion sensing as well as other techniques can be use used in thedetection and/or predict of occupancy, as is described further in thecommonly assigned U.S. Ser. No. 12/881,430, supra. According to someembodiments, occupancy information is used in generating an effectiveand efficient scheduled program. Preferably, an active proximity sensor970A is provided to detect an approaching user by infrared lightreflection, and an ambient light sensor 970B is provided to sensevisible light. The proximity sensor 970A can be used to detect proximityin the range of about one meter so that the thermostat 900 can initiate“waking up” when the user is approaching the thermostat and prior to theuser touching the thermostat. Such use of proximity sensing is usefulfor enhancing the user experience by being “ready” for interaction assoon as, or very soon after the user is ready to interact with thethermostat. Further, the wake-up-on-proximity functionality also allowsfor energy savings within the thermostat by “sleeping” when no userinteraction is taking place our about to take place. The ambient lightsensor 970B can be used for a variety of intelligence-gatheringpurposes, such as for facilitating confirmation of occupancy when sharprising or falling edges are detected (because it is likely that thereare occupants who are turning the lights on and off), and such as fordetecting long term (e.g., 24-hour) patterns of ambient light intensityfor confirming and/or automatically establishing the time of day.

According to some embodiments, for the combined purposes of inspiringuser confidence and further promoting visual and functional elegance,the thermostat 900 is controlled by only two types of user input, thefirst being a rotation of the outer ring 912 as shown in FIG. 99A(referenced hereafter as a “rotate ring” or “ring rotation” input), andthe second being an inward push on an outer cap 908 (see FIG. 9B) untilan audible and/or tactile “click” occurs (referenced hereafter as an“inward click” or simply “click” input). For the embodiment of FIGS.9A-9B, the outer cap 908 is an assembly that includes all of the outerring 912, cover 914, electronic display 916, and metallic portion 924.When pressed inwardly by the user, the outer cap 908 travels inwardly bya small amount, such as 0.5 mm, against an interior metallic dome switch(not shown), and then springably travels back outwardly by that sameamount when the inward pressure is released, providing a satisfyingtactile “click” sensation to the user's hand, along with a correspondinggentle audible clicking sound. Thus, for the embodiment of FIGS. 9A-9B,an inward click can be achieved by direct pressing on the outer ring 912itself, or by indirect pressing of the outer ring by virtue of providinginward pressure on the cover 914, metallic portion 914, or by variouscombinations thereof. For other embodiments, the thermostat 900 can bemechanically configured such that only the outer ring 912 travelsinwardly for the inward click input, while the cover 914 and metallicportion 924 remain motionless. It is to be appreciated that a variety ofdifferent selections and combinations of the particular mechanicalelements that will travel inwardly to achieve the “inward click” inputare within the scope of the present teachings, whether it be the outerring 912 itself, some part of the cover 914, or some combinationthereof. However, it has been found particularly advantageous to providethe user with an ability to quickly go back and forth betweenregistering “ring rotations” and “inward clicks” with a single hand andwith minimal amount of time and effort involved, and so the ability toprovide an inward click directly by pressing the outer ring 912 has beenfound particularly advantageous, since the user's fingers do not need tobe lifted out of contact with the device, or slid along its surface, inorder to go between ring rotations and inward clicks. Moreover, byvirtue of the strategic placement of the electronic display 916centrally inside the rotatable ring 912, a further advantage is providedin that the user can naturally focus their attention on the electronicdisplay throughout the input process, right in the middle of where theirhand is performing its functions. The combination of intuitive outerring rotation, especially as applied to (but not limited to) thechanging of a thermostat's setpoint temperature, conveniently foldedtogether with the satisfying physical sensation of inward clicking,together with accommodating natural focus on the electronic display inthe central midst of their fingers' activity, adds significantly to anintuitive, seamless, and downright fun user experience. Furtherdescriptions of advantageous mechanical user-interfaces and relateddesigns, which are employed according to some embodiments, can be foundin U.S. Ser. No. 13/033,573, supra, U.S. Ser. No. 29/386,021, supra, andU.S. Ser. No. 13/199,108, supra.

FIG. 9C illustrates a cross-sectional view of a shell portion 909 of aframe of the thermostat of FIGS. 9A-B, which has been found to provide aparticularly pleasing and adaptable visual appearance of the overallthermostat 900 when viewed against a variety of different wall colorsand wall textures in a variety of different home environments and homesettings. While the thermostat itself will functionally adapt to theuser's schedule as described herein and in one or more of the commonlyassigned incorporated applications, supra, the outer shell portion 909is specially configured to convey a “chameleon” quality orcharacteristic such that the overall device appears to naturally blendin, in a visual and decorative sense, with many of the most common wallcolors and wall textures found in home and business environments, atleast in part because it will appear to assume the surrounding colorsand even textures when viewed from many different angles. The shellportion 909 has the shape of a frustum that is gently curved when viewedin cross-section, and comprises a sidewall 976 that is made of a clearsolid material, such as polycarbonate plastic. The sidewall 976 isbackpainted with a substantially flat silver- or nickel-colored paint,the paint being applied to an inside surface 978 of the sidewall 976 butnot to an outside surface 977 thereof. The outside surface 977 is smoothand glossy but is not painted. The sidewall 976 can have a thickness Tof about 1.5 mm, a diameter d1 of about 78.8 mm at a first end that isnearer to the wall when mounted, and a diameter d2 of about 81.2 mm at asecond end that is farther from the wall when mounted, the diameterchange taking place across an outward width dimension “h” of about 22.5mm, the diameter change taking place in either a linear fashion or, morepreferably, a slightly nonlinear fashion with increasing outwarddistance to form a slightly curved shape when viewed in profile, asshown in FIG. 9C. The outer ring 912 of outer cap 908 is preferablyconstructed to match the diameter d2 where disposed near the second endof the shell portion 909 across a modestly sized gap g1 therefrom, andthen to gently arc back inwardly to meet the cover 914 across a smallgap g2. It is to be appreciated, of course, that FIG. 9C onlyillustrates the outer shell portion 909 of the thermostat 900, and thatthere are many electronic components internal thereto that are omittedfrom FIG. 9C for clarity of presentation, such electronic componentsbeing described further hereinbelow and/or in other ones of the commonlyassigned incorporated applications, such as U.S. Ser. No. 13/199,108,supra.

According to some embodiments, the thermostat 900 includes a processingsystem 960, display driver 964 and a wireless communications system 966.The processing system 960 is adapted to cause the display driver 964 anddisplay area 916 to display information to the user, and to receiveruser input via the rotatable ring 912. The processing system 960,according to some embodiments, is capable of carrying out the governanceof the operation of thermostat 900 including the user interface featuresdescribed herein. The processing system 960 is further programmed andconfigured to carry out other operations as described furtherhereinbelow and/or in other ones of the commonly assigned incorporatedapplications. For example, processing system 960 is further programmedand configured to maintain and update a thermodynamic model for theenclosure in which the HVAC system is installed, such as described inU.S. Ser. No. 12/881,463, supra. According to some embodiments, thewireless communications system 966 is used to communicate with devicessuch as personal computers and/or other thermostats or HVAC systemcomponents, which can be peer-to-peer communications, communicationsthrough one or more servers located on a private network, or and/orcommunications through a cloud-based service.

FIGS. 10A-10B illustrate exploded front and rear perspective views,respectively, of the thermostat 900 with respect to its two maincomponents, which are the head unit 1100 and the back plate 1300.Further technical and/or functional descriptions of various ones of theelectrical and mechanical components illustrated herein below can befound in one or more of the commonly assigned incorporated applications,such as U.S. Ser. No. 13/199,108, supra. In the drawings shown, the “z”direction is outward from the wall, the “y” direction is the head-to-toedirection relative to a walk-up user, and the “x” direction is theuser's left-to-right direction.

FIGS. 11A-11B illustrate exploded front and rear perspective views,respectively, of the head unit 1100 with respect to its primarycomponents. Head unit 1100 includes a head unit frame 1110, the outerring 1120 (which is manipulated for ring rotations), a head unit frontalassembly 1130, a front lens 1180, and a front grille 1190. Electricalcomponents on the head unit frontal assembly 1130 can connect toelectrical components on the backplate 1300 by virtue of ribbon cablesand/or other plug type electrical connectors.

FIGS. 12A-12B illustrate exploded front and rear perspective views,respectively, of the head unit frontal assembly 1130 with respect to itsprimary components. Head unit frontal assembly 1130 comprises a headunit circuit board 1140, a head unit front plate 1150, and an LCD module1160. The components of the front side of head unit circuit board 1140are hidden behind an RF shield in FIG. 12A but are discussed in moredetail below with respect to FIG. 15. On the back of the head unitcircuit board 1140 is a rechargeable Lithium-Ion battery 1144, which forone preferred embodiment has a nominal voltage of 3.7 volts and anominal capacity of 560 mAh. To extend battery life, however, thebattery 1144 is normally not charged beyond 450 mAh by the thermostatbattery charging circuitry. Moreover, although the battery 1144 is ratedto be capable of being charged to 4.2 volts, the thermostat batterycharging circuitry normally does not charge it beyond 3.95 volts. Alsovisible in FIG. 21B is an optical finger navigation module 1142 that isconfigured and positioned to sense rotation of the outer ring 1120. Themodule 1142 uses methods analogous to the operation of optical computermice to sense the movement of a texturable surface on a facing peripheryof the outer ring 1120. Notably, the module 1142 is one of the very fewsensors that is controlled by the relatively power-intensive head unitmicroprocessor rather than the relatively low-power backplatemicroprocessor. This is achievable without excessive power drainimplications because the head unit microprocessor will invariably beawake already when the user is manually turning the dial, so there is noexcessive wake-up power drain anyway. Advantageously, very fast responsecan also be provided by the head unit microprocessor. Also visible inFIG. 21A is a Fresnel lens 1157 that operates in conjunction with a PIRmotion sensor disposes thereunderneath.

FIGS. 13A-13B illustrate exploded front and rear perspective views,respectively, of the backplate unit 1300 with respect to its primarycomponents. Backplate unit 1300 comprises a backplate rear plate 1310, abackplate circuit board 1320, and a backplate cover 1380. Visible inFIG. 22A are the HVAC wire connectors 1322 that include integrated wireinsertion sensing circuitry, and two relatively large capacitors 1324that are used by part of the power stealing circuitry that is mounted onthe back side of the backplate circuit board 1320 and discussed furtherbelow with respect to FIG. 25.

FIG. 14 illustrates a perspective view of a partially assembled headunit front 1100 showing the positioning of grille member 1190 designedin accordance with aspects of the present invention with respect toseveral sensors used by the thermostat. In some implementations, asdescribed further in U.S. Ser. No. 13/119,108, supra, placement ofgrille member 990 over the Fresnel lens 1157 and an associated PIRmotion sensor 334 conceals and protects these PIR sensing elements,while horizontal slots in the grille member 1190 allow the PIR motionsensing hardware, despite being concealed, to detect the lateral motionof occupants in a room or area. A temperature sensor 330 uses a pair ofthermal sensors to more accurately measure ambient temperature. A firstor upper thermal sensor 330 a associated with temperature sensor 330tends to gather temperature data closer to the area outside or on theexterior of the thermostat while a second or lower thermal sensor 330 btends to collect temperature data more closely associated with theinterior of the housing. In one implementation, each of the temperaturesensors 330 a and 330 b comprises a Texas Instruments TMP112 digitaltemperature sensor chip, while the PIR motion sensor 334 comprisesPerkinElmer DigiPyro PYD 1198 dual element pyrodetector.

To more accurately determine the ambient temperature, the temperaturetaken from the lower thermal sensor 330 b is taken into consideration inview of the temperatures measured by the upper thermal sensor 330 a andwhen determining the effective ambient temperature. This configurationcan advantageously be used to compensate for the effects of internalheat produced in the thermostat by the microprocessor(s) and/or otherelectronic components therein, thereby obviating or minimizingtemperature measurement errors that might otherwise be suffered. In someimplementations, the accuracy of the ambient temperature measurement maybe further enhanced by thermally coupling upper thermal sensor 330 a oftemperature sensor 330 to grille member 1190 as the upper thermal sensor330 a better reflects the ambient temperature than lower thermal sensor334 b. Details on using a pair of thermal sensors to determine aneffective ambient temperature is disclosed in U.S. Pat. No. 4,741,476,which is incorporated by reference herein.

FIG. 15 illustrates a head-on view of the head unit circuit board 1140,which comprises a head unit microprocessor 1502 (such as a TexasInstruments AM3703 chip) and an associated oscillator 1504, along withDDR SDRAM memory 1506, and mass NAND storage 1508. For Wi-Fi capability,there is provided in a separate compartment of RF shielding 1534 a Wi-Fimodule 1510, such as a Murata Wireless Solutions LBWA19XSLZ module,which is based on a Texas Instruments WL1270 chipset supporting the802.11 b/g/n WLAN standard. For the Wi-Fi module 1510 there is providedsupporting circuitry 1512 including an oscillator 1514. For ZigBeecapability, there is provided also in a separately shielded RFcompartment a ZigBee module 1516, which can be, for example, a C2530F256module from Texas Instruments. For the ZigBee module 1516 there isprovided supporting circuitry 1518 including an oscillator 1519 and alow-noise amplifier 1520. Also provided is display backlight voltageconversion circuitry 1522, piezoelectric driving circuitry 1524, andpower management circuitry 1526 (local power rails, etc.). Provided on aflex circuit 1528 that attaches to the back of the head unit circuitboard by a flex circuit connector 1530 is a proximity and ambient lightsensor (PROX/ALS), more particularly a Silicon Labs SI1142Proximity/Ambient Light Sensor with an I2C Interface. Also provided arebattery charging-supervision-disconnect circuitry 1532, and spring/RFantennas 1536. Also provided is a temperature sensor 1538 (risingperpendicular to the circuit board in the +z direction containing twoseparate temperature sensing elements at different distances from thecircuit board), and a PIR motion sensor 1540. Notably, even though thePROX/ALS and temperature sensors 1538 and PIR motion sensor 1540 arephysically located on the head unit circuit board 1140, all thesesensors are polled and controlled by the low-power backplatemicrocontroller on the backplate circuit board, to which they areelectrically connected.

FIG. 16 illustrates a rear view of the backplate circuit board 1320,comprising a backplate processor/microcontroller 1602, such as a TexasInstruments MSP430F System-on-Chip Microcontroller that includes anon-board memory 1603. The backplate circuit board 1320 further comprisespower supply circuitry 1604, which includes power-stealing circuitry,and switch circuitry 1606 for each HVAC respective HVAC function. Foreach such function the switch circuitry 1606 includes an isolationtransformer 1608 and a back-to-back NFET package 1610. The use of FETsin the switching circuitry allows for “active power stealing”, i.e.,taking power during the HVAC “ON” cycle, by briefly diverting power fromthe HVAC relay circuit to the reservoir capacitors for a very smallinterval, such as 100 micro-seconds. This time is small enough not totrip the HVAC relay into the “off” state but is sufficient to charge upthe reservoir capacitors. The use of FETs allows for this fast switchingtime (100 micro-seconds), which would be difficult to achieve usingrelays (which stay on for tens of milliseconds). Also, such relays wouldreadily degrade doing this kind of fast switching, and they would alsomake audible noise too. In contrast, the FETS operate with essentiallyno audible noise. Also provided is a combined temperature/humiditysensor module 1612, such as a Sensirion SHT21 module. The backplatemicrocontroller 1602 performs polling of the various sensors, sensingfor mechanical wire insertion at installation, alerting the head unitregarding current vs. setpoint temperature conditions and actuating theswitches accordingly, and other functions such as looking forappropriate signal on the inserted wire at installation.

In accordance with the teachings of the commonly assigned U.S. Ser. No.13/269,501, supra, the commonly assigned U.S. Ser. No. 13/275,307,supra, and others of the commonly assigned incorporated applications,the thermostat 900 represents an advanced, multi-sensing,microprocessor-controlled intelligent or “learning” thermostat thatprovides a rich combination of processing capabilities, intuitive andvisually pleasing user interfaces, network connectivity, andenergy-saving capabilities (including the presently describedauto-away/auto-arrival algorithms) while at the same time not requiringa so-called “C-wire” from the HVAC system or line power from a householdwall plug, even though such advanced functionalities can require agreater instantaneous power draw than a “power-stealing” option (i.e.,extracting smaller amounts of electrical power from one or more HVACcall relays) can safely provide. By way of example, the head unitmicroprocessor 1502 can draw on the order of 250 mW when awake andprocessing, the LCD module 1160 can draw on the order of 250 mW whenactive. Moreover, the Wi-Fi module 1510 can draw 250 mW when active, andneeds to be active on a consistent basis such as at a consistent 2% dutycycle in common scenarios. However, in order to avoid falsely trippingthe HVAC relays for a large number of commercially used HVAC systems,power-stealing circuitry is often limited to power providing capacitieson the order of 100 mW-200 mW, which would not be enough to supply theneeded power for many common scenarios.

The thermostat 900 resolves such issues at least by virtue of the use ofthe rechargeable battery 1144 (or equivalently capable onboard powerstorage medium) that will recharge during time intervals in which thehardware power usage is less than what power stealing can safelyprovide, and that will discharge to provide the needed extra electricalpower during time intervals in which the hardware power usage is greaterthan what power stealing can safely provide. In order to operate in abattery-conscious manner that promotes reduced power usage and extendedservice life of the rechargeable battery, the thermostat 900 is providedwith both (i) a relatively powerful and relatively power-intensive firstprocessor (such as a Texas Instruments AM3703 microprocessor) that iscapable of quickly performing more complex functions such as driving avisually pleasing user interface display and performing variousmathematical learning computations, and (ii) a relatively less powerfuland less power-intensive second processor (such as a Texas InstrumentsMSP430 microcontroller) for performing less intensive tasks, includingdriving and controlling the occupancy sensors. To conserve valuablepower, the first processor is maintained in a “sleep” state for extendedperiods of time and is “woken up” only for occasions in which itscapabilities are needed, whereas the second processor is kept on more orless continuously (although preferably slowing down or disabling certaininternal clocks for brief periodic intervals to conserve power) toperform its relatively low-power tasks. The first and second processorsare mutually configured such that the second processor can “wake” thefirst processor on the occurrence of certain events, which can be termed“wake-on” facilities. These wake-on facilities can be turned on andturned off as part of different functional and/or power-saving goals tobe achieved. For example, a “wake-on-PROX” facility can be provided bywhich the second processor, when detecting a user's hand approaching thethermostat dial by virtue of an active proximity sensor (PROX, such asprovided by a Silicon Labs SI1142 Proximity/Ambient Light Sensor withI2C Interface), will “wake up” the first processor so that it canprovide a visual display to the approaching user and be ready to respondmore rapidly when their hand touches the dial. As another example, a“wake-on-PIR” facility can be provided by which the second processorwill wake up the first processor when detecting motion somewhere in thegeneral vicinity of the thermostat by virtue of a passive infraredmotion sensor (PIR, such as provided by a PerkinElmer DigiPyro PYD 1198dual element pyrodetector). Notably, wake-on-PIR is not synonymous withauto-arrival, as there would need to be N consecutive buckets of sensedPIR activity to invoke auto-arrival, whereas only a single sufficientmotion event can trigger a wake-on-PIR wake-up.

FIGS. 17A-17C illustrate conceptual examples of the sleep-wake timingdynamic, at progressively larger time scales, that can be achievedbetween the head unit (HU) microprocessor and the backplate (BP)microcontroller that advantageously provides a good balance betweenperformance, responsiveness, intelligence, and power usage. The higherplot value for each represents a “wake” state (or an equivalent higherpower state) and the lower plot value for each represents a “sleep”state (or an equivalent lower power state). As illustrated, thebackplate microcontroller is active much more often for polling thesensors and similar relatively low-power tasks, whereas the head unitmicroprocessor stays asleep much more often, being woken up for“important” occasions such as user interfacing, network communication,and learning algorithm computation, and so forth. A variety of differentstrategies for optimizing sleep versus wake scenarios can be achieved bythe disclosed architecture and is within the scope of the presentteachings. For example, the commonly assigned U.S. Ser. No. 13/275,307,supra, describes a strategy for conserving head unit microprocessor“wake” time while still maintaining effective and timely communicationswith a cloud-based thermostat management server via the thermostat'sWi-Fi facility.

FIG. 18 illustrates a self-descriptive overview of the functionalsoftware, firmware, and/or programming architecture of the head unitmicroprocessor for achieving its described functionalities. FIG. 19illustrates a self-descriptive overview of the functional software,firmware, and/or programming architecture of the backplatemicrocontroller for achieving its described functionalities.

FIG. 20 illustrates a thermostat 2000 according to a preferredembodiment, the thermostat 2000 comprising selected feature combinationsthat have been found to be particularly advantageous for thefacilitation of do-it-yourself thermostat installation, theaccommodation of a variety of different practical installation scenarios(including scenarios where a “C” power wire is not available), theprovisioning of relatively power-intensive advanced interfaces andfunctionalities (e.g., a large visually pleasing electronic display, arelatively powerful general purpose microprocessor, and a reliable Wi-Ficommunications chip) even where a “C” power wire is not available, thefacilitation of operational robustness and durability, compact devicesize, quietness of operation, and other advantageous characteristicsdescribed in the instant disclosure and/or the commonly assignedincorporated applications. In the discussion that follows, the followingHVAC wiring shorthand notations are used: W (heat call relay wire); Y(cooling call relay wire); Rh (heat call relay power); Rc (cooling callrelay power); G (fan call relay wire); O/B (heat pump call relay wire);AUX (auxiliary call relay wire); and C (common wire).

The Rh wire, which leads to one side of the HVAC power transformer (orsimply “HVAC transformer”) that is associated with a heating call relay,can go by different names in the art, which can include heating callswitch power wire, heat call power return wire, heat return wire, returnwire for heating, or return for heating. The Rc wire, which leads to oneside of the HVAC transformer that is associated with a cooling callrelay, can likewise go by different names including cooling call switchpower wire, cooling call power return wire, cooling return wire, returnwire for cooling, or return for cooling. In the case ofsingle-HVAC-transformer systems having both heating and coolingfunctions, it is one and the same HVAC power transformer that isassociated with both the heating call relay and cooling call relay, andin such cases there is just a single wire, usually labeled “R”, leadingback to one side of that HVAC transformer, which likewise can go bydifferent names in the art including call switch power wire, call relaypower wire, call power return wire, power return wire, or simply returnwire.

As illustrated generally in FIG. 20, the thermostat 2000 comprises ahead unit 2002 and a backplate 2004. The backplate 2004 comprises aplurality of FET switches 2006 used for carrying out the essentialthermostat operations of connecting or “shorting” one or more selectedpairs of HVAC wires together according to the desired HVAC operation.The details of FET switches 2006, each of which comprises a dualback-to-back FET configuration, can be found elsewhere in the instantdisclosure and/or in the commonly assigned U.S. Ser. No. 13/034,674,supra. The operation of each of the FET switches 2006 is controlled by abackplate microcontroller 2008 which can comprise, for example, anMSP430 16-bit ultra-low power RISC mixed-signal microprocessor availablefrom Texas Instruments.

Thermostat 2000 further comprises powering circuitry 2010 that comprisescomponents contained on both the backplate 2004 and head unit 2002.Generally speaking, it is the purpose of powering circuitry 2010 toextract electrical operating power from the HVAC wires and convert thatpower into a usable form for the many electrically-driven components ofthe thermostat 2000. Thermostat 2000 further comprises insertion sensingcomponents 2012 configured to provide automated mechanical andelectrical sensing regarding the HVAC wires that are inserted into thethermostat 2000. Thermostat 2000 further comprises a relativelyhigh-power head unit microprocessor 2032, such as an AM3703 Sitara ARMmicroprocessor available from Texas Instruments, which provides the maingeneral governance of the operation of the thermostat 2000. Thermostat2000 further comprises head unit/backplate environmental sensors2034/2038 (e.g., temperature sensors, humidity sensors, active IR motionsensors, passive IR motion sensors, ambient visible light sensors,accelerometers, ambient sound sensors, ultrasonic/infrasonic soundsensors, etc.), as well as other components 2036 (e.g., electronicdisplay devices and circuitry, user interface devices and circuitry,wired communications circuitry, wireless communications circuitry suchas Wi-Fi and/or ZigBee chips) that are operatively coupled to the headunit microprocessor 2032 and/or backplate microprocessor 2008 andcollectively configured to provide the functionalities described in theinstant disclosure and/or the commonly assigned incorporatedapplications.

The insertion sensing components 2012 include a plurality of HVAC wiringconnectors 2014, each containing an internal springable mechanicalassembly that, responsive to the mechanical insertion of a physical wirethereinto, will mechanically cause an opening or closing of one or morededicated electrical switches associated therewith. Exemplaryconfigurations for each of the HVAC wiring connectors 2014 can be foundin the commonly assigned U.S. Ser. No. 13/034,666, supra. With respectto the HVAC wiring connectors 2014 that are dedicated to the C, W, Y,Rc, and Rh terminals, those dedicated electrical switches are, in turn,networked together in a manner that yields the results that areillustrated in FIG. 20 by the blocks 2016 and 2018. For clarity ofpresentation in FIG. 20, the block 2016 is shown as being coupled to theinternal sensing components 2012 by virtue of double lines termed“mechanical causation,” for the purpose of denoting that the output ofblock 2016 is dictated solely by virtue of the particular combination ofHVAC wiring connectors 2014 into which wires have been mechanicallyinserted. More specifically, the output of block 2016, which is providedat a node 2019, is dictated solely by virtue of the particularcombination of C, W, and Y connectors into which wires have beenmechanically inserted. Still more specifically, the output of block 2016at node 2019 is provided in accordance with the following rules: if awire is inserted into the C connector, then the node 2019 becomes the Cnode regardless of whether there are any wires inserted into the Y or Wconnectors; if no wire is inserted into the C connector and a wire isinserted into the Y connector, then the node 2019 becomes the Y noderegardless of whether there is a wire inserted into the W connector; andif no wire is inserted into either of the C or Y connectors, then thenode 2019 becomes the W node. Exemplary configurations for achieving thefunctionality of block 2016 (as combined with components 2012 and wiringconnectors 2014) can be found elsewhere in the instant disclosure and/orin the commonly assigned U.S. Ser. No. 13/034,678, supra. It is to beappreciated that, although mechanical causation for achieving thefunctionality of block 2016 (as combined with components 2012 and wiringconnectors 2014) has been found to be particularly advantageous forsimplicity and do-it-yourself (“DIY”) foolproofing, in other embodimentsthere can be similar functionalities carried out electrically,magnetically, optically, electro-optically, electro-mechanically, etc.without departing from the scope of the present teachings. Thus, forexample, similar results could be obtained by using optically,electrically, and/or magnetically triggered wire insertion sensingcomponents that are coupled to relays or electronic switches that carryout the functionality of block 2016 (as combined with components 2012and wiring connectors 2014) without departing from the scope of thepresent teachings.

Likewise, for clarity of presentation in FIG. 20, the block 2018 is alsoshown as being coupled to the internal sensing components 2012 by virtueof double lines termed “mechanical causation,” for the purpose ofdenoting that its operation, which is either to short the Rc and Rhnodes together or not to short the Rc and Rh nodes together, is dictatedsolely by virtue of the particular combination of HVAC wiring connectors2014 into which wires have been mechanically inserted. Morespecifically, whether the block 2018 will short, or not short, the Rcand Rh nodes together is dictated solely by virtue of the particularcombination of Rc and Rh connectors into which wires have beenmechanically inserted. Still more specifically, the block 2018 will keepthe Rc and Rh nodes shorted together, unless wires have been insertedinto both the Rc and Rh connectors, in which case the block 2018 willnot short the Rc and Rh nodes together because a two-HVAC-transformersystem is present. Exemplary configurations for achieving thefunctionality of block 2018 (as combined with components 2012 and wiringconnectors 2014) can be found elsewhere in the instant disclosure and/orin the commonly assigned U.S. Ser. No. 13/034,674, supra. It is to beappreciated that, although mechanical causation for achieving thefunctionality of block 2018 (as combined with components 2012 and wiringconnectors 2014) has been found to be particularly advantageous forsimplicity and do-it-yourself (“DIY”) foolproofing, in other embodimentsthere can be similar functionalities carried out electrically,magnetically, optically, electro-optically, electro-mechanically, etc.,in different combinations, without departing from the scope of thepresent teachings. Thus, for example, similar results could be obtainedby using optically, electrically, and/or magnetically triggered wireinsertion sensing components that are coupled to relays or electronicswitches that carry out the functionality of block 2018 (as combinedwith components 2012 and wiring connectors 2014) without departing fromthe scope of the present teachings.

As illustrated in FIG. 20, the insertion sensing circuitry 2012 is alsoconfigured to provide electrical insertion sensing signals 2013 to othercomponents of the thermostat 2000, such as the backplate microcontroller2008. Preferably, for each of the respective HVAC wiring terminal 2014,there is provided at least two signals in electrical form to themicrocontroller 2008, the first being a simple “open” or “short” signalthat corresponds to the mechanical insertion of a wire, and the secondbeing a voltage or other level signal (in analog form or, optionally, indigitized form) that represents a sensed electrical signal at thatterminal (as measured, for example, between that terminal and aninternal thermostat ground node). Exemplary configurations for providingthe sensed voltage signal can be found elsewhere in the instantdisclosure and/or in the commonly assigned U.S. Ser. No. 13/034,674,supra. The first and second electrical signals for each of therespective wiring terminals can advantageously be used as a basis forbasic “sanity checking” to help detect and avoid erroneous wiringconditions. For example, if there has been a wire inserted into the “C”connector, then there should be a corresponding voltage level signalsensed at the “C” terminal, and if that corresponding voltage levelsignal is not present or is too low, then an error condition isindicated because there should always be a voltage coming from one sideof the HVAC power transformer (assuming that HVAC system power is on, ofcourse). As another example, if there has been a wire inserted into the“O/B” connector (heat pump call relay wire) but no wire has beeninserted into the “Y” connector (cooling call relay wire), then an errorcondition is indicated because both of these wires are needed for properheat pump control. Exemplary ways for conveying proper and/or improperwiring status information to the user can be found elsewhere in theinstant disclosure and/or in the commonly assigned U.S. Ser. No.13/269,501, supra.

Basic operation of each of the FET switches 2006 is achieved by virtueof a respective control signal (OFF or ON) provided by the backplatemicrocontroller 2008 that causes the corresponding FET switch 2006 to“connect” or “short” its respective HVAC lead inputs for an ON controlsignal, and that causes the corresponding FET switch 2006 to“disconnect” or “leave open” or “open up” its respective HVAC leadinputs for an OFF control signal. For example, the W-Rh FET switch keepsthe W and Rh leads disconnected from each other unless there is anactive heating call, in which case the W-Rh FET switch shorts the W andRh leads together. As a further example, the Y-Rc FET switch keeps the Yand Rc leads disconnected from each other unless there is an activecooling call, in which case the Y-Rc FET switch shorts the Y and Rcleads together. (There is one exception to this basic operation for theparticular case of “active power stealing” that is discussed in moredetail infra, in which case the FET switch corresponding to the HVAClead from which power is being stolen is opened up for very briefintervals during an active call involving that lead. Thus, ifpower-stealing is being performed using the Y lead, then during anactive cooling call the Y-Rc FET switch is opened up for very briefintervals from time to time, these brief intervals being short enoughsuch that the Y HVAC relay does not un-trip.)

Advantageously, by virtue of the above-described operation of block2018, it is automatically the case that for single-transformer systemshaving only an “R” wire (rather than separate Rc and Rh wires as wouldbe present for two-transformer systems), that “R” wire can be insertedinto either of the Rc or Rh terminals, and the Rh-Rc nodes will beautomatically shorted to form a single “R” node, as needed for properoperation. In contrast, for dual-transformer systems, the insertion oftwo separate wires into the respective Rc and Rh terminals will causethe Rh-Rc nodes to remain disconnected to maintain two separate Rc andRh nodes, as needed for proper operation. The G-Rc FET switch keeps theG and Rc leads disconnected from each other unless there is an activefan call, in which case the G-Rc FET switch shorts the G and Rc leadstogether (and, advantageously, the proper connection will be achievedregardless of whether the there is a single HVAC transformer or dualHVAC transformers because the Rc and Rh terminals will be automaticallyshorted or isolated accordingly). The AUX-Rh FET switch keeps the AUXand Rh leads disconnected from each other unless there is an active AUXcall, in which case the AUX-Rh FET switch shorts the AUX and Rh leadstogether (and, advantageously, the proper connection will be achievedregardless of whether the there is a single HVAC transformer or dualHVAC transformers because the Rc and Rh terminals will be automaticallyshorted or isolated accordingly). For heat pump calls, the O/B-Rc FETswitch and Y-Rc FET switch are jointly operated according to therequired installation-dependent convention for forward or reverseoperation (for cooling or heating, respectively), which convention canadvantageously be determined automatically (or semi-automatically usingfeedback from the user) by the thermostat 2000 as described further inthe commonly assigned PCT/US12/30084, supra.

Referring now to the powering circuitry 2010 in FIG. 20, advantageouslyprovided is a configuration that automatically adapts to the poweringsituation presented to the thermostat 2000 at the time of installationand thereafter in a manner that has been found to provide a goodcombination of robustness, adaptability, and foolproofness. The poweringcircuitry 2010 comprises a full-wave bridge rectifier 2020, a storageand waveform-smoothing bridge output capacitor 2022 (which can be, forexample, on the order of 30 microfarads), a buck regulator circuit 2024,a power-and-battery (PAB) regulation circuit 9528, and a rechargeablelithium-ion battery 2030. In conjunction with other control circuitryincluding backplate power management circuitry 2027, head unit powermanagement circuitry 2029, and the microcontroller 2008, the poweringcircuitry 2010 is configured and adapted to have the characteristics andfunctionality described hereinbelow. Description of further details ofthe powering circuitry 2010 and associated components can be foundelsewhere in the instant disclosure and/or in the commonly assigned U.S.Ser. No. 13/034,678, supra, and U.S. Ser. No. 13/267,871, supra.

By virtue of the configuration illustrated in FIG. 20, when there is a“C” wire presented upon installation, the powering circuitry 2010operates as a relatively high-powered, rechargeable-battery-assistedAC-to-DC converting power supply. When there is not a “C” wirepresented, the powering circuitry 2010 operates as a power-stealing,rechargeable-battery-assisted AC-to-DC converting power supply. Asillustrated in FIG. 20, the powering circuitry 2010 generally serves toprovide the voltage Vcc MAIN that is used by the various electricalcomponents of the thermostat 2000, and that in one embodiment willusually be about 4.0 volts. As used herein, “thermostat electrical powerload” refers to the power that is being consumed by the variouselectrical components of the thermostat 2000. Thus, the general purposeof powering circuitry 2010 is to judiciously convert the 24 VACpresented between the input leads 2019 and 2017 to a steady 4.0 VDCoutput at the Vcc MAIN node to supply the thermostat electrical powerload. Details relating to bootstrap circuitry (not shown), whose purposeis to provide a kind of cruder, less well-regulated, lower-levelelectrical power that assists in device start-up and that can act as akind of short term safety net, are omitted from the present discussionfor purposes of clarity of description, although further information onsuch circuitry can be found in U.S. U.S. Ser. No. 13/034,678, supra.

Operation of the powering circuitry 2010 for the case in which the “C”wire is present is now described. Although the powering circuitry 2010may be referenced as a “power-stealing”circuit in the general sense ofthe term, the mode of operation for the case in which the “C” wire ispresent does not constitute “power stealing” per se, because there is nopower being “stolen” from a wire that leads to an HVAC call relay coil(or to the electronic equivalent of an HVAC call relay coil for somenewer HVAC systems). For the case in which the “C” wire is present,there is no need to worry about accidentally tripping (for inactivepower stealing) or untripping (for active power stealing) an HVAC callrelay, and therefore relatively large amounts of power can be assumed tobe available from the input at nodes 2019/2017. When the 24 VAC inputvoltage between nodes 2019 and 2017 is rectified by the full-wave bridgerectifier 2020, a DC voltage at node 2023 is present across the bridgeoutput capacitor 2022, and this DC voltage is converted by the buckregulator 2024 to a relatively steady voltage, such as 4.45 volts, atnode 2025, which provides an input current I_(BP) to thepower-and-battery (PAB) regulation circuit 2028.

The microcontroller 2008 controls the operation of the poweringcircuitry 2010 at least by virtue of control leads leading between themicrocontroller 2008 and the PAB regulation circuit 2028, which for oneembodiment can include an LTC4085-3 chip available from LinearTechnologies Corporation. The LTC4085-3 is a USB power manager andLi-Ion/Polymer battery charger originally designed for portablebattery-powered applications. The PAB regulation circuit 2028 providesthe ability for the microcontroller 2008 to specify a maximum valueI_(BP)(max) for the input current I_(BP). The PAB regulation circuit2028 is configured to keep the input current at or below I_(BP)(max),while also providing a steady output voltage Vcc, such as 4.0 volts,while also providing an output current Icc that is sufficient to satisfythe thermostat electrical power load, while also tending to the chargingof the rechargeable battery 2030 as needed when excess power isavailable, and while also tending to the proper discharging of therechargeable battery 2030 as needed when additional power (beyond whatcan be provided at the maximum input current I_(BP)(max)) is needed tosatisfy the thermostat electrical power load. If it is assumed for thesake of clarity of explanation that the voltages at the respectiveinput, output, and battery nodes of the PAB regulation circuit 2028 areroughly equal, the functional operation of the PAB regulation circuit2028 can be summarized by relationship I_(BP)=Icc+I_(BAT), where it isthe function of the PAB regulation circuit 2028 to ensure that I_(BP)remains below I_(BP)(max) at all times, while providing the necessaryload current Icc at the required output voltage Vcc even for cases inwhich Icc is greater than I_(BP)(max). The PAB regulation circuit 2028is configured to achieve this goal by regulating the value of I_(BAT) tocharge the rechargeable battery 2030 (I_(BAT)>0) when such charge isneeded and when Icc is less than I_(BP)(max), and by regulating thevalue of I_(BAT) to discharge the rechargeable battery 2030 (I_(BAT)<0)when Icc is greater than I_(BP)(max).

For one embodiment, for the case in which the “C” wire is present, thevalue of I_(BP)(max) for the PAB regulation circuit 2028 is set to arelatively high current value, such as 100 mA, by the microcontroller2008. Assuming a voltage of about 4.45 volts at node 2025, thiscorresponds to a maximum output power from the buck regulator 2024 ofabout 445 mW. Advantageously, by virtue of the rechargeablebattery-assisted operation described above, the powering circuitry 2010can provide instantaneous thermostat electrical power load levels higherthan 445 mW on an as-needed basis by discharging the rechargeablebattery, and then can recharge the rechargeable battery once theinstantaneous thermostat electrical power load goes back down. Generallyspeaking, depending especially on the instantaneous power usage of thelarge visually pleasing electronic display (when activated by the usercoming close or manipulating the user interface), the high-poweredmicroprocessor 2032 (when not in sleep mode), and the Wi-Fi chip (whentransmitting), the instantaneous thermostat electrical power load canindeed rise above 445 mW by up to several hundred additional milliwatts.For preferred embodiments in which the rechargeable battery 2030 has acapacity in the several hundreds of milliamp-hours (mAh) at or near thenominal Vcc voltage levels (e.g., 560 mAh at 3.7 volts), supplying thisamount of power is generally not problematic, even for extended timeperiods (even perhaps up to an hour or more), provided only that thereare sufficient periods of lower-power usage below 445 mW in which therechargeable battery 2030 can be recharged. The thermostat 2000 isconfigured such that this is easily the case, and indeed is designedsuch that the average power consumption is below a much lower thresholdpower than this, as discussed further below in the context of “activepower stealing.”

Operation of the powering circuitry 2010 for the case in which the “C”wire is not present is now described. For such case, in accordance withthe above-described operation of insertion sensing components/switches2012/2016, it will be the Y-lead that is connected to the node 2019 if a“Y” wire has been inserted, and it will otherwise be the W-lead that isconnected to the node 2019 if no “Y” wire has been inserted. Stateddifferently, it will be the Y-lead from which “power is stolen” if a “Y”wire has been inserted, and it will otherwise be the W-lead from which“power is stolen” if no “Y” wire has been inserted. As used herein,“inactive power stealing” refers to the power stealing that is performedduring periods in which there is no active call in place based on thelead from which power is being stolen. Thus, for cases where it is the“Y” lead from which power is stolen, “inactive power stealing” refers tothe power stealing that is performed when there is no active coolingcall in place. As used herein, “active power stealing” refers to thepower stealing that is performed during periods in which there is anactive call in place based on the lead from which power is being stolen.Thus, for cases where it is the “Y” lead from which power is stolen,“active power stealing” refers to the power stealing that is performedwhen there is an active cooling call in place.

Operation of the powering circuitry 2010 for “inactive power stealing”is now described. In the description that follows it will be assumedthat the “Y” wire has been inserted and therefore that power is to bestolen from the Y-lead, with it being understood that similarcounterpart operation based on the “W” lead applies if no “Y” wire hasbeen inserted and power is to be stolen from the W-lead. During inactivepower stealing, power is stolen from between the “Y” wire that appearsat node 2019 and the Rc lead that appears at node 2017. As discussedpreviously, the Rc lead will be automatically shorted to the Rh lead (toform a single “R” lead) for a single-HVAC transformer system, while theRc lead will be automatically segregated from the Rh lead for adual-HVAC transformer system. In either case, there will be a 24 VACHVAC transformer voltage present across nodes 2019/2017 when no coolingcall is in place (i.e., when the Y-Rc FET switch is open). For oneembodiment, the maximum current I_(BP)(max) is set to a relativelymodest value, such as 20 mA, for the case of inactive power stealing.Assuming a voltage of about 4.45 volts at node 2025, this corresponds toa maximum output power from the buck regulator 2024 of about 90 mW. Thepower level of 90 mW has been found to be a generally “safe” powerstealing level for inactive power stealing, where the term “safe” isused to indicate that, at such power level, all or virtually all HVACcooling call relays that are installed in most residential andcommercial HVAC systems will not accidentally trip into an “on” statedue to the current following through the cooling call relay coil. Duringthis time period, the PAB regulator 2028 operates to discharge thebattery 2030 during any periods of operation in which the instantaneousthermostat electrical power load rises above 90 mW, and to recharge thebattery (if needed) when the instantaneous thermostat electrical powerload drops below 90 mW. Provided that the rechargeable battery 2030 isselected to have sufficient capacity (such as 560 mAh at 3.7 volts asdiscussed above), supplying power at above 90 mW (even several hundredmilliwatts more) is generally not problematic even for extended timeperiods (even perhaps up to an hour or more), provided only that thereare sufficient periods of lower-power usage below 90 mW in which therechargeable battery 2030 can be recharged. The thermostat 2000 isconfigured such that the average power consumption is well below 90 mW,and indeed for some embodiments is even below 10 mW on a long term timeaverage.

According to one embodiment, the powering circuitry 2010 is furthermonitored and controlled during inactive power stealing by themicrocontroller 2008 by virtue of monitoring the voltage V_(BR) acrossthe bridge output capacitor 2022 at node 2023 that leads into the buckregulator 2024. For the embodiment of FIG. 20, the voltage VBR ismonitored directly by virtue of an analog to digital converter (“ADC”)that is built into the microcontroller 2008. According to an embodiment,the voltage V_(BR) across the bridge output capacitor 2022 can bemonitored, either on a one-time basis, a periodic basis, or a continuousbasis to assess a general “strength” of the HVAC system with respect tothe power that can be safely provided during inactive power stealing.This assessment can then be used to adjust a determination for themaximum “safe” amount of power that can be provided at the output ofbuck regulator 2024 during inactive power stealing, which can in turn beimplemented by the microcontroller 2008 by setting the maximum inputcurrent I_(BP)(max) of the PAB regulator 2028 for inactive powerstealing. In one particularly advantageous embodiment, at the outset ofan inactive power stealing period (either on a one-time basis afterthermostat installation or on ongoing basis as desired), themicrocontroller 2008 initially sets the maximum current I_(BP)(max) tozero and measures the resultant voltage V_(BR). This “open-circuit”value of V_(BR) will typically be, for example, somewhere around 30volts. The microcontroller 2008 then sets the maximum currentI_(BP)(max) to 20 mA and measures the resultant voltage V_(BR). If thevalue of V_(BR) when I_(BP)(max)=20 mA remains roughly the same as itsopen-circuit value (less than a predetermined threshold difference, forexample), then it is determined that the HVAC system is “strong enough”at the Y-lead to accommodate a higher value for the maximum currentI_(BP)(max), and the microcontroller 2008 increases the maximum currentI_(BP)(max) to 40 mA (corresponding to a maximum “safe” power stealinglevel of about 180 mW assuming 4.45 volts). On the other hand, if thevalue of V_(BR) when I_(BP)(max)=20 mA tends to sag relative to itsopen-circuit value (greater than the predetermined threshold difference,for example), then it is determined that the HVAC system is not “strongenough” at the Y-lead to accommodate an increased maximum currentI_(BP)(max), and its value will remain fixed at 20 mA. Optionally, thisprocess can be repeated to further increase the maximum currentI_(BP)(max) to successively higher levels, although care should be takento ensure by empirical testing with a target population of HVAC systemsthat the cooling call relay will not be tripped at such higher levelsduring inactive power stealing. For one embodiment, the process stopswhen I_(BP)(max)=40 mA, to avoid accidental cooling call relay trippingacross a very large population of HVAC systems.

Operation of the powering circuitry 2010 for “active power stealing” isnow described. In the description that follows it will be assumed thatthe “Y” wire has been inserted and therefore that power is to be stolenfrom the Y-lead, with it being understood that similar counterpartoperation based on the “W” lead applies if no “Y” wire has beeninserted. During an active cooling call, it is necessary for current tobe flowing through the HVAC cooling call relay coil sufficient tomaintain the HVAC cooling call relay in a “tripped” or ON state at alltimes during the active cooling call. In the absence of power stealing,this would of course be achieved by keeping the Y-Rc FET switch 2006 inON state at all times to short the Y and Rc leads together. To achieveactive power stealing, the microcontroller 2008 is configured by virtueof circuitry denoted “PS MOD” to turn the Y-Rc FET switch OFF for smallperiods of time during the active cooling call, wherein the periods oftime are small enough such that the cooling call relay does not“un-trip” into an OFF state, but wherein the periods of time are longenough to allow inrush of current into the bridge rectifier 2020 to keepthe bridge output capacitor 2022 to a reasonably acceptable operatinglevel. For one embodiment, this is achieved in a closed-loop fashion inwhich the microcontroller 2008 monitors the voltage V_(BR) at node 2023and actuates the signal Y-CTL as necessary to keep the bridge outputcapacitor 2022 charged. By way of example, during active power stealingoperation, the microcontroller 2008 will maintain the Y-Rc FET switch inan ON state while monitoring the voltage V_(BR) until it drops below acertain lower threshold, such as 8 volts. At this point in time, themicrocontroller 2008 will switch the Y-Rc FET switch into an OFF stateand maintain that OFF state while monitoring the voltage V_(BR), whichwill rise as an inrush of rectified current charges the bridge capacitor2022. Then once the voltage V_(BR) rises above a certain upperthreshold, such as 10 volts, the microcontroller 2008 will turn the Y-RcFET switch back into in an ON state, and the process continuesthroughout the active power stealing cycling. Although the scope of thepresent teachings is not so limited, the microcontroller 2008 ispreferably programmed to keep the maximum current I_(BP)(max) to arelatively modest level, such as 20 mA (corresponding to a maximum“safe” power stealing level of about 90 mW assuming 4.45 volts)throughout the active power stealing cycle. The circuit elements aredesigned and configured such that the ON-OFF cycling of the Y-Rc FETswitch occurs at a rate that is much higher than 60 Hz and generally hasno phase relationship with the HVAC power transformer, whereby thespecter of problems that might otherwise occur due to zero crossings ofthe 24 VAC voltage signal are avoided. By way of example and not by wayof limitation, for some embodiments the time interval required forcharging the bridge output capacitor 2022 from the lower threshold of 8volts to the upper threshold of 10 volts will be on the order 10 to 100microseconds, while the time that it takes the bridge output capacitor2022 to drain back down to the lower threshold of 8 volts will be on theorder of 1 to 10 milliseconds. It has been found that, advantageously,at these kinds of rates and durations for the intermittent “OFF” stateof the Y-Rc FET switch 2006, there are very few issues brought about byaccidental “un-tripping” of the HVAC cooling call relay during activepower stealing across a wide population of residential and commercialHVAC installations.

According to one embodiment, it has been found advantageous to introducea delay period, such as 60-90 seconds, following the instantiation of anactive cooling cycle before instantiating the active power stealingprocess. This delay period has been found useful in allowing manyreal-world HVAC systems to reach a kind of “quiescent” operating statein which they will be much less likely to accidentally un-trip away fromthe active cooling cycle due to active power stealing operation of thethermostat 2000. According to another embodiment, it has been foundfurther advantageous to introduce another delay period, such as 60-90seconds, following the termination of an active cooling cycle beforeinstantiating the inactive power stealing process. This delay period haslikewise been found useful in allowing the various HVAC systems to reacha quiescent state in which accidental tripping back into an activecooling cycle is avoided. Preferably, the microcontroller 2008implements the above-described instantiation delays for both active andinactive power stealing by setting the maximum current I_(BP)(max) tozero for the required delay period. In some embodiments, the operationof the buck regulator circuit 2024 is also shut down for approximatelythe first 10 seconds of the delay period to help ensure that the amountof current being drawn by the powering circuitry 2010 is very small.Advantageously, the rechargeable-battery-assisted architecture of thepowering circuitry 2010 readily accommodates the above-describedinstantiation delays in that all of the required thermostat electricalpower load can be supplied by the rechargeable battery 2030 during eachof the delay periods.

Referring now to the flowchart 2100 in FIG. 21, advantageously providedis a method for incorporating a delay period as described above. Themethod may generally be considered to describe incorporating a delayperiod for any transition between operating states of an HVAC system. Inone embodiment, at least some of the circuit elements described inrelation to FIG. 20 may be combined to form what may be termed a“powering circuit” that is coupled to the HVAC wire connectors and isconfigured to provide electrical load power to the thermostat processingand control circuit as described above. The powering circuit may includea power control circuit, such as the MSP430 processor 2008. The powercontrol circuit may be configured to receive signals that indicate theoperating state of the HVAC system. As described above, the poweringcircuit may include a rechargeable battery.

Generally, an HVAC system may operate in at least two differentoperating states (such as a first state and a second state) relative toa particular call relay wire. For example, an HVAC system may operate inan active state. As used herein, the term “active state” relative to aparticular call relay wire may include any state in which the HVACsystem is actively calling for an HVAC function (e.g., heating, cooling,fan, etc.) using the particular call relay wire. In the example of FIG.20, connecting the “Y” wire to the “Rc” wire by closing the Y-R_(C) FETswitch may cause the HVAC system to enter into an active state of airconditioning an environment; therefore the HVAC system could beconsidered to be in the active state relative to the “Y” wire.Alternatively, connecting the “W” wire to the “Rh” wire by closing theY-R_(H) FET switch may cause the HVAC system to enter into an activestate of heating an environment; therefore, the HVAC system could beconsidered to be in an active state relative to the “W” wire. As usedherein, the term “inactive state” relative to a particular call relaywire may include any state in which the HVAC system is not activelycalling for an HVAC function (e.g., heating, cooling, fan, etc.) usingthe particular call relay wire. For example, the inactive state relativeto the “Y” wire may include times when the thermostat is not activelycalling for a cooling function using the “Y” wire, including times whenthe thermostat is actively calling for a heating function using the “W”call relay wire. Either the inactive state or the active state may bereferred to herein as a first state or a second state interchangeably,or a first operating state and a second operating state, depending onthe embodiment.

It also should be noted that the HVAC system may be performing anenvironmental functions such as heating, cooling, etc., yet not be“active” relative to a particular call relay wire. For example, the HVACsystem may be calling for a heating function using the “W” wire. In thiscase, the HVAC system is not in an “active” state in relation to the “Y”call relay wire. Therefore, the thermostat may continue inactive powerstealing (as defined above) on the “Y” call relay wire while the HVACsystem is performing a heating function using the “W” wire. In theembodiments discussed below where power stealing is suspended, reduced,or minimized during transitions between operating states, the transitionbetween operating states is with respect to the wire from which thepower stealing takes place. In one embodiment, transitions betweenoperating states respective to a call relay wire other than the callrelay wire from which power stealing takes place may not require thepower stealing to be suspended.

The method of flowchart 2100 may include determining that the HVACsystem is transitioning from a first state to a second state (2102).Such a determination may be made by sensing the internal operations ofthe thermostat. Alternatively or additionally, the determination may bemade by receiving a signal any of the other systems within thethermostat, depending on the embodiment. In one embodiment, a thermostatprocessing and control circuit, such as the AM3703 processor 2032 ofFIG. 20, may initiate a transition between operating states. Thethermostat processing and control circuit may then send a signal to thepower control circuit indicating that the HVAC system is transitioningbetween states. In one case, the first state may comprise an activestate, and the second state may comprise an inactive state.Alternatively, the first state may comprise the inactive state and thesecond state may comprise the active state.

The method may further include reducing the power stolen from the HVACsystem (2104). In one embodiment, power is being stolen from the sameHVAC system call relay wire that is being used to transition the HVACsystem between operating states. This reduction in power may beinitiated in response to the received signal indicating a transitionbetween operating states. In one embodiment, the purpose of reducing thepower stolen from the HVAC system may be to allow the switchingcircuitry of the HVAC system, often including relays, to stabilize. Inother words, the power extraction/stealing described extensivelyelsewhere in this disclosure may be reduced, minimized, and/or halted inorder to allow the HVAC system to stabilize.

In one embodiment, the operation of the buck regulator 2024 may bestopped, thereby stopping the power harvesting altogether. In anotherembodiment, instead of stopping the power harvesting altogether, thepower may be reduced to a level that is less likely to interfere withthe transitioning operation of the HVAC system. For example, thepowering circuit may cause the power extraction circuit to limit itspower harvesting operations to a predetermined current level. In theembodiment of FIG. 20, the MSP430 processor 2008 may send a signal tothe LTC4085 chip 2028 instructing it to limit the value of I_(BP) to amaximum threshold current level. The threshold current level may bedetermined experimentally and may depend on the particular HVAC system.In one embodiment, the thermostat may automatically determine the propercurrent threshold by testing various values during a transition betweenoperating states. In another embodiment, I_(BP) may be limited to amaximum of 1 mA. In yet another embodiment, I_(BP) may be limited to arange of 1 mA to 4 mA. In yet another embodiment, I_(BP) may be reducedto a value of less than 1 mA, then gradually increased to a highervalue, such as 5 mA, during the transition. In this embodiment, I_(BP)may be referred to as a current associated with the power that isstolen.

The method may further include maintaining the reduced power stealinglevel throughout a delay period (2106). As used herein, such a delayperiod may also be referred to as a time period, a first time period, asecond time period, a first delay period, a second delay period, and soforth. Although not explicitly shown in FIG. 21, the reduced powerextracted from the HVAC system need not be held at a constant levelthroughout the delay period. In one embodiment, the power can be reducedimmediately and can be immediately restored after the delay period hasexpired, like a step function. In another embodiment, the power may begradually reduced at the beginning of the delay period and/or graduallyincreased at the end of the delay period. The length of the delay periodmay vary based on the type of transition and/or the specific embodimentand will be discussed further below.

The method may additionally include increasing the power stolen from theHVAC system after the delay period has ended (2108). Again, powerstealing may be associated with the same call relay wire that is used totransition the thermostat between operating states. In one embodiment,the power harvesting level may return to the same level that it was atprior to it being reduced. In another embodiment, the power harvestinglevel may be increased to a level that depends on the current state ofthe HVAC system. For example, the power extracted from the HVAC systemduring an active state may be different than the power extracted fromthe HVAC system during the inactive state. Furthermore, the way in whichpower is extracted may vary based on the operating state of the HVACsystem. As described extensively elsewhere in this disclosure, the levelof stolen power may be increased during an active state by increasing aswitching rate of one or more of the FET switches 2006 such that the FEToff-time is still a small percentage of the FET on-time. During the FEToff-time, the power stealing may be carried out as it is when the HVACsystem is in the inactive state. Alternatively or additionally, thelevel of harvested power may be increased during an inactive state byincreasing I_(BP).

In the embodiment of FIG. 20, the HVAC wire from which power isharvested is chosen using mechanical causation, which is described abovein this disclosure. In this particular implementation, the thermostatattempts to use the “C” wire if it is available. If the “C” wire is notavailable, then the thermostat attempts to use the “Y” for the HVACcooling system. If the “Y” wire is not available, then the thermostatattempts to use the “W” wire for the HVAC heating system. Which of thesewires is selected can be determined simply through the mechanicalconnections that are established between the HVAC wires and the HVACwire connectors on the thermostat. This mechanical configuration isusually determined at the time of installation.

However, in another embodiment (not shown), the HVAC wire that isselected for power harvesting may be software selected. In other words,the operations embodied by box 2016 in FIG. 20 may be replaced by one ormore software processes. In the embodiments described above, the powerstealing is carried out using the same HVAC connector that is used toinitiate the transition between operating states. However, in anotherembodiment, the thermostat may be configured to dynamically selectbetween available call relay wires, depending on the HVAC function. Forexample, the MSP430 processor 2008 may be configured to switch betweenthe “Y” and “W” wires depending on the operation of the HVAC system. Inone embodiment, the power control circuit may determine that the “Y”wire should be selected for power harvesting during an HVAC heatingcycle where the “W” wire is being actively used to call for the HVACfunction. Similarly, the power control circuit may determine that the“W” wire should be selected for power harvesting during an HVAC coolingcycle where the “Y” wire is being actively used to call for the HVACfunction. It should be noted that if a “C” wire is available duringinstallation, then switching between HVAC wires for power harvesting maynot be needed in this embodiment, and delay periods may not be neededwhen the HVAC system transitions between operating states.

It has been found that some embodiments may benefit from using a firstdelay period for transitions between the active state to the inactivestate relative a call relay wire, while using a second delay period fortransitions between the inactive state to the active state relative to acall relay wire, where the first and second delay periods are different.Referring now to FIG. 22, a flowchart 2200 is provided that illustratesa method for utilizing different delay periods depending on theoperating states that the HVAC system is transitioning between. Themethod of flowchart 2200 may be considered a specific implementation ofthe general flowchart 2100 of FIG. 21. Instead of generically referringto a first and second state, flowchart 2200 specifically calls out thedifferent types of transitions between states and implements a differentdelay period for each type of transition.

The method may include determining that the HVAC system is transitioningbetween states (2202). The method may also include reducing the powerstolen from the HVAC system (2204). These two steps may be similar tothose of FIG. 21 described above. The method may additionally includedetermining whether the HVAC system is transitioning from the activestate to the inactive state relative to the call relay wire from whichpower is being stolen (2206). This determination may be made by thethermostat processing and control circuit, the powering circuit, and/orthe power control circuit. If the HVAC system is transitioning from theactive state to the inactive state relative to the call relay wire fromwhich power is being stolen, then the method may further includeutilizing a first delay period (2208). The HVAC wire connector that isused in the power stealing may also be used by the thermostat to causethe transition between the HVAC functions.

The length of the first delay period may be characterized in a number ofdifferent ways, depending on the specific embodiment. In one embodiment,the first delay period may be approximately 10 seconds. In anotherembodiment, the first delay period may be at least 5 seconds but lessthan 20 seconds. In yet another embodiment, the first delay period maybe characterized in relation to the time that the HVAC system operatesin the inactive state. For example, the first delay period could becharacterized as being substantially less in duration than the durationof the inactive state. In yet another embodiment, the first delay periodcan be characterized in relation to the period of the AC signal receivedfrom the HVAC connectors. For example, the delay period could be between60 and 600 times the AC period. In most households, the AC signal fromthe HVAC system will oscillate at a frequency of 60 Hz, which wouldyield a first delay period of 1 to 6 seconds. Note that the first delayperiod described in relation to FIG. 22 is specific to a transition fromthe active state to the inactive state, whereas the delay perioddescribed in relation to FIG. 21 should be generically interpreted tocover a delay between any two states.

If, instead of transitioning from the active state to the inactivestate, it is determined that the HVAC system is transitioning from theinactive state to the active state relative to the call relay wire fromwhich power is being stolen, then the method may further includeutilizing a second delay period (2210). As was the case with the lengthof the first delay period, the length of the second delay period may becharacterized in a number of different ways, depending on the specificembodiment. In one embodiment, the second delay period may beapproximately 50 seconds. In another embodiment, the second delay periodmay be at least 40 seconds but less than 160 seconds. In anotherembodiment, the second delay period may be approximately 70 to 80seconds. In yet another embodiment, the second delay period may becharacterized in relation to the time that the HVAC system operates inthe active state. For example, the second delay period could becharacterized as being substantially less in duration than the durationof the active state. Alternatively, the second delay period can becharacterized as percentage of the average active cycle of the HVACsystem. In yet another embodiment, the second delay period can becharacterized in relation to the period of the AC signal received fromthe HVAC connectors. For example, the second period could be between1800 and 10500 times the AC period. In most households, the AC signalfrom the HVAC system will oscillate at a frequency of 60 Hz, which wouldyield a second delay period of 30 to 175 seconds. In yet anotherembodiment, the second delay period may comprise a predetermined timethat is shorter than the first delay period. In other words, the delaywill be longer for a transition from the active to the inactive statethan it is for a transition from the inactive to the active state.

After the expiration of the first delay period or the second delayperiod, depending on the transition type, the method may additionallyinclude increasing the power extracted from the HVAC system (2212). Asdescribed previously, the power may increase quickly like a stepfunction, may ramp up slowly, may return to a previously extracted powerlevel, and/or may establish a new extracted power level based on thestatus of the HVAC system and/or inputs from the powering circuit.According to one specific embodiment, the power level may be increasedbased on a value of capacitor 2022 from FIG. 20 by measuring a value forV_(BR) and comparing this voltage value to one or more predeterminedthresholds. In another embodiment, the power level may be increasedbased on a measured current value in the powering circuit, such asI_(BP) and/or I_(CC). Other techniques for determining an extractedpower level may also be used as described elsewhere in this disclosure.

For some embodiments, operation of the power stealing circuitry of FIG.20 may proceed as follows. At a first typical point in time during itsongoing operation, the thermostat 2000 may be in an inactive state withrespect to the selected power-stealing call relay wire. The inactivestate may have lasted anywhere from several minutes to several hours orbeyond, although by virtue of known HVAC operating principles includingfactors such as temperature maintenance bands, compressor lock-outintervals, and so forth, the inactive state will usually not be lessthan about 5 minutes long. During this inactive state, the powerstealing proceeds according to the inactive power stealing methodsdescribed above. During this inactive state, a typical average HVACcharge current being supplied into the powering circuitry 2010 may be inthe range of 8-16 mA, the buck regulator 2024 will be in an on state,and the current I_(BP) being supplied to the PAB regulation circuit 2028may be in the range of 8-16 mA. For this inactive state, the overallcurrent passing through the coil of the selected call relay may be inthe 8-16 mA range. When it comes time for the HVAC system to enter intoan active state with respect to the selected power-stealing call relaywire (for example, an active heating call for cases in which theselected power-stealing call relay wire is a “W” wire, an active coolingcall for cases in which the selected power-stealing call relay wire is a“Y” wire, an active fan call for cases in which the selectedpower-stealing call relay wire is a “G” wire, an active auxiliary powercall for cases in which the selected power-stealing call relay wire isan “AUX” wire, and so on), which determination may be made by the headunit microprocessor 2032 responsive to operative setpoints and ambientconditions and communicated to the backplate microcontroller 2008, thereis preferably a suspension of power stealing activity for a firstsuspension interval that may last for a period of between 80-90 seconds.For a first portion of this first suspension interval, the first portionbeing about 10 seconds, the buck regulator 2024 may be turned into anoff state by the backplate microcontroller 2008 (over command/controllines not shown in FIG. 20), and the value of I_(BP)(max) of the PABregulation circuit 2028 may be set to zero by the backplatemicrocontroller 2008. For this first portion of the first suspensioninterval, the HVAC charge current being supplied into the poweringcircuitry 2010 will be zero, and the current I_(BP) being supplied tothe PAB regulation circuit 2028 will be zero. For this first portion ofthe first suspension interval, the overall average current passingthrough the coil of the selected call relay may be in the 50-1500 mArange, which is representative of a typical amount of current that manycall relay coils will experience when they are activating theirrespective HVAC function in many common HVAC systems. For a secondportion of the first suspension interval, the second portion being about70-80 seconds, the buck regulator 2024 may be placed into an on state,and the value of I_(BP)(max) may be set to a very low value, such asless than 1 mA. During this second portion of the first suspensioninterval, which may be termed an active precharge interval, a typicalaverage HVAC charge current being supplied into the powering circuitry2010 may be very small, such as less than 1 mA, and the current I_(BP)being supplied to the PAB regulation circuit 2028 may be may be verysmall, such as less than 1 mA. During this second portion of the firstsuspension interval, the overall current passing through the coil of theselected call relay may be in the 50-1500 mA range. During the secondportion of the first suspension interval, by virtue of the small amountof current I_(BP), there is caused to be a small amount of current goinginto the buck regulator 2024 that is sufficient to keep acurrent-limiting/soft-start circuit (not shown) in front of the buckregulator 2024 from undesirably opening up. During the first suspensioninterval, the power needed to supply the Vcc operating power to thethermostat electronic circuitry is supplied solely by the rechargeablebattery 2030 (with the minor exception of the very small trickle ofprecharge-related power coming from the buck regulator 2024 during thesecond portion of the first suspension interval). Following the firstsuspension interval, whose duration of roughly 80-90 seconds has beenfound sufficient to allow transient behavior of most HVAC systems tosettle down enough such that active power stealing will not result inundesired un-tripping of the selected call relay, the active powerstealing process occurs according to the active power stealing methodsdescribed above in the instant specification. During this active powerstealing interval, a typical average HVAC charge current being suppliedinto the powering circuitry 2010 may be about 8 mA, the buck regulator2024 will be in an on state, and the current I_(BP) being supplied tothe PAB regulation circuit 2028 may be about 20 mA. For this activestate of power stealing, the overall current passing through the coil ofthe selected call relay may be in the 50-1500 mA range. Depending on theparticular environmental state of the enclosure in which the HVAC systemis installed, the active power stealing state may last anywhere fromseveral minutes (such as for many forced air systems in moderate climateconditions operating in a maintenance temperature band) to several hours(such as for radiant systems in more extreme climate conditions afterlong periods of low-energy settings). When it comes time for the HVACsystem to enter back into an inactive state with respect to the selectedpower-stealing call relay wire, which determination may be made by thehead unit microprocessor 2032 responsive to operative setpoints andambient conditions and communicated to the backplate microcontroller2008, there is preferably a suspension of power stealing activity for asecond suspension interval that may last for a period of about 10seconds. Generally speaking, the second suspension interval (associatedwith an active-to-inactive transition) can often be selected to besubstantially less than the first suspension interval (associated withan inactive-to-active transition) because the inactive state of theselected call relay will usually be more robust against transienttripping than its active state will be against un-tripping whenoperating under control of the thermostat 2000. For the secondsuspension interval, the buck regulator 2024 may be turned into an offstate and the value of I_(BP)(max) set to zero by the backplatemicrocontroller 2008. For this second suspension interval, the HVACcharge current being supplied into the powering circuitry 2010 will bezero, and the current I_(BP) being supplied to the PAB regulationcircuit 2028 will be zero. During the second suspension interval, thepower needed to supply the Vcc operating power to the thermostatelectronic circuitry is supplied solely by the rechargeable battery2030. Subsequent to the second suspension interval, the inactivepower-stealing state will again resume, which corresponds to the firsttypical point in time above, and the cycle may then continue for theduration of the operation of the thermostat 2000.

Whereas many alterations and modifications of the present invention willno doubt become apparent to a person of ordinary skill in the art afterhaving read the foregoing description, it is to be understood that theparticular embodiments shown and described by way of illustration are inno way intended to be considered limiting. Therefore, reference to thedetails of the preferred embodiments is not intended to limit theirscope.

What is claimed is:
 1. A thermostat, comprising: at least one Heating, Ventilation, and Air Conditioning (HVAC) wire connector configured to receive at least one HVAC wire including at least one call relay wire; a powering circuit, including an energy-storage device, that is coupled to said at least one call relay wire and configured to provide electrical power to the thermostat by power stealing therefrom, said power stealing including an active power stealing mode and an inactive power stealing mode; wherein said powering circuit is configured to substantially suspend said power stealing for at least a first time interval when transitioning from the inactive power stealing mode to the active power stealing mode; and wherein said powering circuit provides said electrical power to the thermostat during said times of substantially suspended power stealing at least in part by drawing power from said energy-storage device.
 2. The thermostat of claim 1, wherein said suspended power stealing comprises stealing a first amount of power that is very small or negligible in comparison to a second amount of power that is stolen during times when said power stealing is not suspended.
 3. The thermostat of claim 1, wherein said suspended power stealing comprises reducing a current associated with the power that is stolen to less than approximately 1 mA.
 4. The thermostat of claim 1, wherein: said powering circuit is also configured to substantially suspend said power stealing for at least a second time interval immediately following a transition from the active power stealing mode to the inactive power stealing mode, said second time interval being sufficiently long to ensure an absence of transient signals that could lead to undesired call relay tripping or untripping; and said second time interval is between approximately 5 seconds to approximately 20 seconds.
 5. The thermostat of claim 1, wherein said power stealing is suspended for between approximately 40 seconds to approximately 160 seconds for said transition from said inactive power stealing mode to said active power stealing mode.
 6. The thermostat of claim 1, wherein during said active power stealing mode a connection between (i) said at least one call relay wire and (ii) a corresponding return HVAC wire is disconnected for periods lasting at least a second time period, wherein the second time period during which said connection is disconnected is substantially less than a third time period during which said connection is connected during said active power stealing mode.
 7. The thermostat of claim 1, wherein the thermostat is configured to: detect whether a common “C” wire is inserted in the thermostat; provide, if the common “C” wire is inserted in the thermostat, electrical power for use by the thermostat by taking power from said common “C” wire at all times of operation and without any suspensions thereof associated with transitions between said active and inactive power stealing modes; provide, if no common “C” wire is inserted in the thermostat, electrical power for use by the thermostat by taking power from said at least one call relay wire by said power stealing.
 8. The thermostat of claim 7, wherein the thermostat is further configured to: select a “Y” cooling call wire as said at least one call relay wire from which power is taken by said power stealing if (i) no common “C” wire is inserted in the thermostat, and (ii) a “Y” cooling call wire is inserted in the thermostat; and select a “W” heating call wire as said at least one call relay wire from which power is taken by said power stealing if (i) no common “C” wire is inserted in the thermostat, (ii) no “Y” cooling call wire is inserted in the thermostat, and (iii) a “W” heating call wire is inserted in the thermostat.
 9. A thermostat, comprising: at least one HVAC (heating, ventilation, and air conditioning) wire connector configured to receive at least one HVAC wire including at least one call relay wire; a powering circuit, including an energy-storage device, that is coupled to the at least one call relay wire and configured to provide electrical power to the thermostat by power stealing therefrom, said power stealing including an active power stealing mode and an inactive power stealing mode; wherein said powering circuit is configured to substantially suspend said power stealing for a first time interval when transitioning from the inactive power stealing mode to the active power stealing mode, wherein said first time interval is at least 5 seconds.
 10. The thermostat of claim 9, wherein said suspended power stealing comprises stealing a first amount of power that is very small or negligible in comparison to a second amount of power that is stolen during times when said power stealing is not suspended.
 11. The thermostat of claim 9, wherein said suspended power stealing comprises reducing a current associated with the power that is stolen to less than approximately 1 mA.
 12. The thermostat of claim 9, wherein: said powering circuit is also configured to substantially suspend said power stealing for at least a second time interval immediately following a transition from the active power stealing mode to the inactive power stealing mode, said second time interval being sufficiently long to ensure an absence of transient signals that could lead to undesired call relay tripping or untripping; and said second time interval is between approximately 5 seconds to approximately 20 seconds.
 13. The thermostat of claim 9, wherein said power stealing is suspended for between approximately 40 seconds to approximately 160 seconds for each said transition from said inactive power stealing mode to said active power stealing mode.
 14. The thermostat of claim 9, wherein the thermostat is configured to: detect whether a common “C” wire is inserted in the thermostat; provide, if the common “C” wire is inserted in the thermostat, electrical power for use by the thermostat by taking power from said common “C” wire at all times of operation and without any suspensions thereof associated with transitions between said active and inactive power stealing modes; provide, if no common “C” wire is inserted in the thermostat, electrical power for use by the thermostat by taking power from said at least one call relay wire by said power stealing.
 15. A method of powering a thermostat coupled to an HVAC (heating, ventilation, and air conditioning) system, the method comprising: receiving at least one HVAC wire including at least one call relay wire; providing electrical power to the thermostat by power stealing from said at least one call relay wire, said power stealing including an active power stealing mode and an inactive power stealing mode; and substantially suspending said power stealing for at least a first time interval following a transition from the second operating mode to the first operating mode; and providing said electrical power to the thermostat during said times of substantially suspended power stealing at least in part by drawing power from an energy-storage device of the thermostat.
 16. The method of claim 15, wherein said first time interval is at least approximately 5 seconds.
 17. The method of claim 15, wherein said first time interval is at least approximately 75 seconds.
 18. The method of claim 15, wherein said substantially suspending said power stealing comprises reducing a downstream current level associated with the power stealing to less than approximately 5 mA.
 19. The method of claim 15, wherein said substantially suspending said power stealing comprises completely suspending said power stealing by reducing a downstream current level associated with the power stealing to less than approximately 0.1 mA.
 20. The method of claim 15, further comprising: detecting whether a common “C” wire is inserted in the thermostat; providing, if the common “C” wire is inserted in the thermostat, electrical power for use by the thermostat by taking power from said common “C” wire at all times of operation and without any suspensions thereof associated with transitions between said active and inactive power stealing modes; providing, if no common “C” wire is inserted in the thermostat, electrical power for use by the thermostat by carrying said power stealing from said at least one call relay wire. 